Impact resistant blends of thermoplastic polyesters and modified block copolymers

ABSTRACT

A toughened multiphase thermoplastic composition is provided by incorporating at least one functionalized, selectively hydrogenated alkenyl arene/conjugated diene block copolymer to which has been grafted an effective amount of carboxyl functional groups primarily in the alkenyl arene blocks thereof with a thermoplastic polyester. The carboxyl functional groups may be in the form of carboxylic acids, their salts, their esters, and combinations of two or more of these.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 140,008, filed Dec. 31, 1987,now abandoned, which is a continuation-in-part of U.S. patentapplication Ser. No. 766,216, filed Aug. 16, 1985, now U.S. Pat. No.4,797,447.

FIELD OF THE INVENTION

The present invention relates to an impact resistant polymericcomposition. More particularly, it relates to an impact resistantpolymeric composition comprising a polyester and a modified blockcopolymer. The copolymer is obtained by modifying a base block copolymercomposed of a selectively hydrogenated conjugated diene polymer blockand an alkenyl arene polymer block with a carboxyl containing functionalgroup grafted primarily in the alkenyl arene block. These carboxylgroups may then be esterified and/or neutralized with a metal ion tovary the degree of impact modification on the polymeric composition.

BACKGROUND OF THE INVENTION

Thermoplastic polyesters, such as poly(1,4-butylene terephthalate) (PBT)and poly(ethylene terephthalate) (PET) are a class of materials whichpossess a good balance of properties comprising good elongation, highstrength, high energy to break and stiffness which make them useful asstructural materials. However, thermoplastic polyesters are quitesensitive to crack propagation. Consequently, a major deficiency ofthermoplastic polyesters is their poor resistance to impact and theirtendency to break in a brittle rather than ductile manner.

In general, improvements in the impact resistance of thermoplasticresins have been achieved by incorporating a low modulus rubber.Moreover, good dispersion of the rubber phase as well as developingadhesion between the rubber and matrix contribute to efficient impactmodification of these resins.

It is well known to those skilled in the art that hydrogenated blockcopolymers of styrene and butadiene possess many of the propertiesuseful for impact modification of plastics. These low modulus rubbermaterials display a PG,3 low glass transition temperature, acharacteristic advantage for optimum toughening at lower temperatures.Furthermore, these block copolymers contain little unsaturation whichfacilitates their blending with high processing temperature plasticswithout degradation of the elastomer phase.

Block copolymers are unique impact modifiers compared to other rubbersin that they contain blocks which are microphase separated over therange of applications and processing conditions. These polymer segmentsmay be tailored to become miscible with the resin to be modified. Goodparticle-matrix adhesion is obtained when different segments of theblock copolymer reside in the matrix and in the rubber phase. Thisbehavior is observed when hydrogenated block copolymers of styrene andbutadiene are blended with resins such as polyolefins and polystyrene.Impact properties competitive with high impact polystyrene are obtaineddue to the compatibility of polystyrene with the polystyrene endblock ofthe block copolymer. Other polyolefins are toughened due to enhancedcompatibility with the rubber segment.

Although the hydrogenated block copolymers do have many of thecharacteristics required for plastic impact modification, thesematerials are deficient as impact modifiers for many materials which aredissimilar in structure to styrene or hydrogenated butadiene. Inparticular, significant improvement in the impact resistance ofpolyesters with the addition of these hydrocarbon polymers has not beenachieved. This result is due to poor interfacial interaction between theblend components and poor dispersion of the rubber particles. Poorinterfacial adhesion affords areas of severe weakness in articlesmanufactured from such blends which when under impact result in facilemechanical failure.

The placement of functional groups onto the block copolymer may providesites for interactions with such polar resins and, hence may extend therange of applicability of this elastomer. Such interactions, whichinclude chemical reaction, hydrogen bonding and dipole interactions, area route to achieving improved interfacial adhesion and particledispersion, hence improved impact modification of polar thermoplastics.

Many attempts have been made to improve the impact properties ofpolyesters by adding low modulus modifiers which contain polar moietiesas a result of polymerization or which have been modified to containpolar moieties by various grafting techniques. To this end, variouscompositions have been proposed utilizing such modifiers havingcarboxylic acid moieties and derivatives thereof, for example, Epsteinin U.S. Pat. No. 4,172,859; Saito et al. in German Offenlegungsschrift3,022,258 (published Jan. 8, 1981); and Shiraki et al. in U.S. Pat. Nos.4,628,072 and 4,657,971.

Epstein discloses a broad range of low modulus polyester modifiers whichhave been prepared by free radical copolymerization of specific monomerswith acid containing monomers. Alternatively, Epstein discloses themodification of polymers by grafting thereto specific carboxylic acidcontaining monomers. The grafting techniques allowed for therein arelimited to thermal addition (ene reaction) and to nitrene insertion intoC--H bonds or addition to C═C bonds (ethylenic unsaturation). ThoughEpstein does disclose a broad range of polyester modifiers, Epstein doesnot disclose or suggest the utilization of hydrogenated copolymers ofalkenyl arenes and conjugated dienes nor, more particularly, modifiedselectively hydrogenated copolymers of alkenyl arenes and conjugateddienes as polyester modifiers.

Saito et al. disclose thermoplastic polyester compositions which containa modified unsaturated aromatic vinyl compound/conjugated diene blockcopolymer as a polyester modifier. The unsaturated block copolymer hasbeen modified by grafting a dicarboxylic acid group or derivativethereof (e.g. anhydride moieties) at a point of ethylenic unsaturationvia thermal addition (ene reaction). However, such modifiers andcompositions containing same are deficient in that the weatherabilityand resistance to thermal deterioration are poor; and, therefore, thepolymers and compositions have been used only in the fields where suchproperties are not required. Furthermore, it is also noted that the enereaction is a reversible reaction.

Shiraki et al. also describe a polyester composition containing a blockcopolymer similar to that of Saito et al. However, in order to improvethe weatherability and resistance to heat aging, Shiraki et al.partially hydrogenate the block copolymer in their respective blends toan ethylenic unsaturation degree not exceeding 20 percent of theethylenic unsaturation contained in the block copolymer prior tohydrogenation. Once the block copolymer is partially hydrogenated, theblock copolymer is modified by grafting a molecular unit containing acarboxylic acid group and/or a group derived therefrom (e.g. anhydridemoieties).

As is readily apparent in each of the foregoing prior art polyestercompositions utilizing alkenyl arene/conjugated diene block copolymersas polyester modifiers, improved impact modification of the particularpolyester is achieved via specific interactions, between the modifieddiene block and the polyester.

On the otherhand, Gergen et al., in the copending U.S. Pat. No.4,797,447, describe a polyester composition containing a block copolymerwhich is a thermally stable, modified, selectively hydrogenated, high1,2 content alkenyl arene/conjugated diene block copolymer grafted withat least one functional group utilizing the metalation process. Therein,the functional groups are grafted primarily in the alkenyl arene block.In this composition, interactions between the polyester and rubber areachieved via the alkenyl arene block.

Further research and experimentation on polyester compositionscontaining the modified block copolymers of Gergen et al. in copendingU.S. Pat. No. 4,797,447 have yielded unexpected and significant impactproperty improvements. These new polyester blend compositions containblock copolymers having the carboxyl functional groups present in eitheror any of their acid, ester and neutralized metal carboxylate saltforms. Whether either or any of these forms in combination produceimprovements may be dependent on the particular polyester(s) selected.Furthermore, the impact properties are also improved by increasing thedegree of carboxyl functionality.

To those skilled in the art, the degree to which the grafting reactionand particle size reduction occur, thereby promoting interfacialadhesion, together with the dispersion of the rubber within the blendtypically contribute to impact toughening of the blend. The resultsherein demonstrate that functionalizing the alkenyl arene segmentpromotes covalent bonding or a strong interaction between the modifiedblock copolymer and the polyester. Furthermore, the block copolymer alsobecomes well dispersed in the polyester phase.

In the compositions disclosed herein, ionic crosslinking is presentwithin the alkenyl arene block domains within the modifier present inthe polyester blend composition. The function of the ionic crosslinkingwithin the modifier phase is not entirely understood as it pertains tothe properties of the blend composition.

The neutralization effect herein is to be distinguished from ioniccrosslinking as is disclosed in Rees, U.S. Pat. No. 3,264,272; Saito etal., U.S. Pat. No. 4,429,076; and Gergen et al., U.S. Pat. No.4,578,429. Rees and Gergen et al. ('429) utilize ionic crosslinkingsolely to improve the properties of the pure hydrocarbon polymer asopposed to improving the properties of polyester blend compositions.

Rees is limited to ionic crosslinking in homopolymer systems in whichthe carboxyl groups are distributed throughout the homopolymer molecule.As such, Rees does not deal with copolymers and resulting alkenyl arenedomain formation. On the otherhand, though Gergen et al. ('429)addresses block copolymers, the carboxyl groups are distributedthroughout the elastomeric diene block rather than the alkenyl areneblocks.

Saito et al. utilize ionic crosslinking to improve the properties ofmodified block copolymer which are to be blended with a thermoplasticpolymer having a polar group thereby improving the impact resistance andhardness of the blend. In Saito et al., the block copolymer is modifiedby grafting maleic anhydride onto the conjugated diene portion thereof.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a toughenedmultiphase thermoplastic composition comprising a thermoplasticpolyester and a modified alkenyl arene/conjugated diene block copolymerwherein an effective amount of carboxyl functional groups for tougheningthe multiphase thermoplastic composition are grafted to the blockcopolymer primarily in the alkenyl arene block. It has been surprisinglyfound that the existence of the carboxylic acid and carboxylate esterand/or salt (neutralized, e.g. --COOLi) forms of the carboxyl functionalgroups either singly or in combination produces significant improvementsin the impact properties of the overall blend. The composition istoughened by a modified block copolymer preferably having a phase sizein the range of about 0.01 to about 2 μm, preferably about 0.05 to about1.5 μm, more preferably about 0.1 to about 1.0 μm, and being adhered tothe polyester. Phase size is the mean cross-sectional size of cells inan interpenetrating network or of discrete particles in a dispersedsystem.

More particularly, there is provided a toughened multiphasethermoplastic composition comprising:

(a) one phase containing a thermoplastic polyester; and

(b) at least one other phase containing at least one functionalized,selectively hydrogenated block copolymer to which has been grafted onthe average an effective amount of carboxyl functional groups fortoughening said multiphase thermoplastic composition, saidfunctionalized block copolymer comprising

(1) a base block copolymer which comprises

(i) at least one polymer block A, said A block being predominantly apolymerized alkenyl arene block, and

(ii) at least one selectively hydrogenated polymer block B, said B blockprior to hydrogenation being predominantly a polymerized conjugateddiene block,

(2) wherein substantially all of said carboxyl functional groups aregrafted to said base block copolymer on said A blocks,

(c) said one phase (a) being present in a weight ratio of about 50:50 upto about 99:1 relative to said at least one other phase (b), preferablyabout 60:40 up to about 95:5 and more preferably about 70:30 up to about90:10.

These carboxyl functional groups may be in the form of carboxylic acids,their salts and esters, and combinations thereof.

The functionalized block copolymer is preferably characterized as havingbeen prepared by the process which comprises

metalating the base block copolymer, and

reacting the resulting metalated base block copolymer with effectiveamounts of at least one graftable electrophilic molecule containing atleast one of said carboxyl functional groups or with effective amountsof an electrophile, wherein the electrophile is carbon dioxide, therebypreparing the functionalized block copolymer.

Furthermore, the functionalized block copolymer may be linear orbranched, with the term "branched" also including symmetric orasymmetric radial and star structures.

The effective amount of carboxyl functional groups for toughening thecomposition is on the average at least about one (1) carboxyl functionalgroups per molecule of the block copolymer. It is presently believedthat the addition of about one (1) carboxyl functional group peraromatic ring of the A blocks is limiting. Preferably, the carboxylfunctional groups grafted to the functionalized block copolymer arepresent from about 0.02% w to about 20.0% w, more preferably from about0.1% w to about 10.0% w and yet more preferably from about 0.2% w toabout 5.0% w, based on said base block copolymer.

Preferably, each of these carboxyl functional groups may be either inthe carboxylic acid or ester form or ionized by neutralization withmetal ions having a positive ionized valence state. Thus, from 100percent to 0 percent of the carboxyl functional groups may be in theacid form (--COOH); and, correspondingly, from 0 percent to 100 percentof the carboxyl functional group may be in the ester and/or salt form(neutralized, e.g. --COOLi). The metal ions may be selected from thegroup consisting of uncomplexed and complexed metal ions. Preferably,the metal ions have a positive ionized valence state of from one tothree inclusive.

Preferably, there is provided the toughened multiphase thermoplasticcomposition as defined above, wherein

(a) each of the A blocks prior to hydrogenation is predominantly apolymerized monoalkenyl monocyclic arene block having an averagemolecular weight of about 1,000 to about 125,000, preferably about 1,000to about 60,000,

(b) each of the B blocks prior to hydrogenation is predominantly apolymerized conjugated diene block having an average molecular weight ofabout 10,000 to about 450,000, preferably about 10,000 to about 150,000,

(c) the A blocks constitute between about 1 and about 99, preferablybetween about 2 and about 60, and more preferably between about 2 and40, percent by weight of the copolymer,

(d) the unsaturation of the B blocks is less than about 10 percent,preferably less than about 5 percent and more preferably at most 2percent, of the original unsaturation of the B blocks,

(e) the unsaturation of the A blocks is greater than about 50 percent,preferably greater than about 90 percent, of the original unsaturationof the A blocks, and

(f) the carboxyl functional group is preferably present on the averagefrom about 0.02% w to about 20.0% w and more preferably on the averagefrom about 0.1% w to about 10.0% w and yet more preferably on theaverage from about 0.2% w to about 5.0% w based on the molecular weightof said base block copolymer.

A feature of this invention lies in providing polymeric compositionswhich are processable in the melt and/or in solution and have improvedmechanical properties, such as impact resistance.

Accordingly, those and other features and advantages of the presentinvention will become apparent from the following detailed description.

IN THE DRAWINGS

FIG. 1 is an x-y plot of 1/8 inch notched izod at room temperature (ft.lb./in.) versus % w block copolymer in a PBT blend.

FIG. 2 is an x-y plot of 1/8 inch notched izod at room temperature (ft.lb./in.) versus the ratio of carboxylate salt to carboxylic aid for PBTblends (30% w block copolymer).

FIG. 3 is an x-y plot of 1/8 inch notched izod at room temperature (ft.lb./in.) versus the ratio of carboxylate salt to carboxylic acid for PBTblends (20% w block copolymer).

FIG. 4 is an x-y plot of block copolymer content (% w) versus the ratioof carboxylate salt to carboxylic acid for PBT blends.

FIG. 5 is an x-y plot of 1/8 inch notched izod at room temperature(ft.-lb./in.) versus the ratio of carboxylate salt to carboxylic acidfor PET blends (20% w block copolymer).

DETAILED DESCRIPTION OF THE INVENTION Polyesters

The thermoplastic polyesters employed in the present invention includepolyesters having a recurring ester linkage in the molecule, forexample, polylactones, and polyesters having a structure formed bypolycondensation of a dicarboxylic acid with a glycol, for example,polyalkylene arylates. The polyesters have a generally crystallinestructure with a melting point over 120° C. or are generally amorphouswith a glass transition temperature above 25° C., and are thermoplasticas opposed to thermosetting. The number average molecular weight of thepolyesters is generally between 5000 to 100,000 and preferably 10,000 to50,000.

One particularly useful group of polyesters are those thermoplasticpolyesters having a structure formed by polycondensation of adicarboxylic acid with a glycol. These polyesters may be preparedaccording to methods well known in the art such as by directesterification or ester exchange reaction of a dicarboxylic acid or thelower alkyl ester, acid halide, or anhydride derivatives thereof with aglycol.

Among the dicarboxylic acids suitable for preparing polyesters useful inthe present invention are those having from 2 to about 25 carbon atomsinclusive, preferably of up to 15 carbon atoms inclusive. Thedicarboxylic acids may be aliphatic containing hydrocarbyl groups suchas alkylene, alkylidene, cycloalkylene, and cycloalkylidene. Thehydrocarbyl groups may contain unsaturation as in carbon-carbon multiplebonds and may be substituted such as an arylaliphatic containing an arylsubstituent on an otherwise aliphatic molecule. Examples of suitablealiphatic dicarboxylic acids are oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, suberic acid, azelaic acid and sebacicacid. The dicarboxylic acids may also be aromatic having at least onearomatic ring, preferably up to two aromatic rings, and the aromaticrings may contain hydrocarbyl substituents. Where the aromaticdicarboxylic acid contains more than one aromatic ring, the rings may beconnected by carbon-carbon bonds, by hydrocarbyl bridging groups such asalkylene or alkylidene groups, or by other bridging groups such as oxo,thio and sulfone. Examples of suitable aromatic dicarboxylic acids areterephthalic acid, isophthalic acid, orthophthalic acid,1,5-naphthalenic dicarboxylic acid, 2,5-naphthalenic dicarboxylic acid,2,6 -naphthalenic dicarboxylic acid, 2,7-naphthalenic dicarboxylic acid,4,4'biphenyldicarboxylic acid, 4,4'dicarboxydiphenylsulfone,4,4'dicarboxydiphenylmethane, 4,4'-dicarboxydiphenylpropane, and4,4'-dicarboxydiphenyloctane. Also suitable for use in the invention aredicarboxylic acids having both an aliphatic carboxylic acid moiety andan aromatic carboxylic acid moiety wherein the two acid moieties areconnected by carbon-carbon bonds, by hydrocarbyl bridging groups such asalkylene or alkylidene groups, or by other bridging groups such as anoxo group. Examples of such suitable dicarboxylic acids are4-carboxyphenylacetic acid, 4-carboxyphenoxyacetic acid,4-carboxyphenoxypropionic acid, 4-carboxyphenoxybutyric acid,4-carboxyphenoxyvaleric acid, 4-carboxyphenoxyhexanoic acid andβ-(2-alkyl-4-carboxyphenoxy)propionic acids. Mixtures of dicarboxylicacids can also be employed. Terephthalic acid is particularly preferred.

The glycols suitable for preparing the polyesters useful in the presentinvention include polyhydric alcohols of 2 to about 12 carbon atoms,preferably dihydric alcohols (diols) such as alkylene glycols andaromatic glycols and dihydroxy ethers. Examples of suitable alkyleneglycols are the straight chain alkylene glycols such as ethylene glycol,1,3-propylene glycol, 1,4-butylene glycol, 1,6-hexylene glycol,2-methyl-1,3-propanedial, 1,10-decamethylene glycol, and1,12-dodecamethylene glycol. Other suitable alkylene glycols arealicyclic diols such as 1,4-cyclohexane dimethanol. Aromatic glycols canbe substituted in whole or in part. Suitable aromatic glycols includearomatic dihydroxy compounds such as p-xylylene glycol, pyrocatechol,resorcinol, hydroquinone, and alkyl-substituted derivatives of thesecompounds. Suitable dihydroxy ethers include diethylene glycol andtriethylene glycol. Preferred glycols are the straight chain alkyleneglycols, more preferred are the straight chain alkylene glycols having 2to 4 carbon atoms.

A preferred group of these polyesters are the poly(alkylene arylates),in particular the poly(alkylene terephthalates) such as the crystallinecopolymers poly(ethylene terephthalate), poly(propylene terephthalate)and poly(butylene terephthalate).

Poly(alkylene terephthalates), an alkylene glycol, may be formed by thepolycondensation of an alkylene glycol and dimethylterephthalate orterephthalic acid. When straight-chained alkylene glycols are utilized,the poly(alkylene terephthalates) have the generalized formula: ##STR1##where m is the number of carbon atoms in the straight-chained alkyleneglycol utilized and n varies from 70 to 280. For example, ethyleneglycol (m=2) is utilized in forming poly(ethylene terephthalate);1,3-propylene glycol (m=3) is utilized in forming poly(propyleneterephthalate); and 1,4-butylene glycol (m=4) is utilized in formingpoly(butylene terephthalate). The molecular weight of thesepoly(alkylene terephthalates) typically varies from about 20,000 toabout 50,000. A suitable process for manufacturing these polymers isdisclosed in U.S. Pat. No. 2,465,319 and in British Pat. No. 1,305,130,which are incorporated herein by reference.

Commercially available poly(ethylene terephthalate) and poly(butyleneterephthalate) are available from General Electric (GE) under thetradename VALOX® thermoplastic polyester. Other commercial polymersinclude CELANEX® from Celanese, TENITE® from Eastman Kodak, and VITUF®(PBT) and CLEARTUF® (PET) from Goodyear Chemical.

Another commerically available and suitable polyester is ARDEL®polyarylate available from Amoco, having repeating units of theformulae: ##STR2##

Another valuable group of thermoplastic polyesters which may be used inthe present invention are polylactones. Polylactones have recurringester structural units such as those obtained by ring openingpolymerization of a cyclic lactone. Examples of suitable polylactonesare poly(pivalolactone), poly(β-propiolactone) and poly(ε-caprolactone).

Polypivalolactone is a linear polymer having recurring ester structuralunits mainly of the formula:

    --[--CH.sub.2 --C(CH.sub.3 --.sub.2 C(O)O--]--

i.e., units derived from pivalolactone. Preferably the polyester is apivalolactone homopolymer. Also included, however, are the copolymers ofpivalolactone with not more than 50 mole percent, preferably not morethan 10 mole percent of other beta-propiolactones, such asbeta-propiolactone; alpha, alpha-diethyl-beta-propiolactone; andalpha-methyl-alpha-ethyl-beta-propiolactone. The term"beta-propiolactones" refers to beta-propiolactone (2-oxetanone) and toderivatives thereof which carry no substituents at the beta-carbon atomof the lactone ring. Preferred beta-propiolactones are those containinga tertiary or quaternary carbon atom in the alpha position relative tothe carbonyl group. Especially preferred are the alpha,alpha-dialkyl-beta-propiolactones wherein each of the alkyl groupsindependently has from one to four carbon atoms. Examples of usefulmonomers are:

alpha-ethyl-alpha-methyl-beta-propiolactone,

alpha-methyl-alpha-isopropyl-beta-propiolactone,

alpha-ethyl-alpha-n-butyl-beta-propiolactone,

alpha-chloromethyl-alpha-methyl-beta-propiolactone,

alpha, alpha-bis(chloromethyl)-beta-propiolactone, and

alpha, alpha-dimethyl-beta-propiolactone (pivalolactone). See generallyU.S. Pat. Nos. 3,259,607; 3,299,171; and 3,579,489 which areincorporated herein by reference. These polypivalolactones have amolecular weight in excess of 20,000 and a melting point in excess of120° C.

Another useful polyester which may be obtained from a cyclic lactone ispolycaprolactone. Typical poly(ε-caprolactones) are substantially linearpolymers in which the repeating unit is ##STR3## These polymers havesimilar properties to the polypivalolactones and may be prepared by asimilar polymerization mechanism. See generally U.S. Pat. No. 3,259,607.

Other useful polyesters include the cellulosics. The thermoplasticcellulosic esters employed herein are widely used as molding, coatingand film-forming materials and are well known. These materials includethe solid thermoplastic forms of cellulose nitrate, cellulose acetate(e.g. cellulose diacetate, cellulose triacetate), cellulose butyrate,cellulose acetate butyrate, cellulose propionate, cellulosetridecanoate, carboxymethyl cellulose, ethyl cellulose, hydroxyethylcellulose and acetylated hydroxyethyl cellulose as described on pages25-28 of Modern Plastics Encyclopedia, 1971-72, and references listedtherein.

Linear and branched polyesters and copolyesters of glycols andterephthalic or isophthalic acid have been commercially available for anumber of years and have been described in U.S. Pat. Nos. 2,465,319 and3,047,539.

Thermoplastic polyesters, such as PBT and PET, are useful as injectionmoldable materials which can be formed into articles which exhibit agood balance of properties including strength and stiffness. However, animprovement in impact strength of these materials is desirable.

The amount of polyester included in the compositions of the presentinvention may vary widely depending upon the properties desired in thecomposition. For example, as great as 99 percent by weight of thecomposition may be composed of polyester. Preferably, the amounts ofpolyester included in the composition may range from about 50 to about99 percent by weight based on total weight of the composition. Morepreferably, the amounts of polyester are from about 60 to about 95percent by weight with a particularly preferred amount being from about70 to about 90 percent by weight, as these amounts appear to impartexcellent impact resistance to the finished composition.

Selectively Hydrogenated Block Copolymer Base Polymer

The selectively hydrogenated block copolymers employed in the presentinvention may have a variety of geometrical structures, since theinvention does not depend on any specific geometrical structure, butrather upon the chemical constitution of each of the polymer blocks, andsubsequent modification of the block copolymer. The precursor of theblock copolymers employed in the present composition are preferablythermoplastic elastomers and have at least one alkenyl arene polymerblock A and at least one elastomeric conjugated diene polymer block B.The number of blocks in the block copolymer is not of special importanceand the macromolecular configuration may be linear or branched, whichincludes graft, radial or star configurations, depending upon the methodby which the block copolymer is formed.

Typical examples of the various structures of the precursor blockcopolymers used in the present invention are represented as follow:

    (A-B)n

    (A-B)n A

    (B-A)n B

    [(A-B)p]m X

    [(B-A)p]m X

    [(A-B)pA]m X

    and

    [(B-A)p B]m X

wherein A is a polymer block of an alkenyl arene, B is a polymer blockof a conjugated diene, X is a residual group of a polyfunctionalcoupling agent having two or more functional groups, n and p are,independently, integers of 1 to 20 and m is an integer of 2 to 20.Furthermore, the above-mentioned branched configurations may be eithersymmetrical or asymmetrical with respect to the blocks radiating from X.

It will be understood that both blocks A and B may be eitherhomopolymer, random or tapered copolymer blocks as long as each blockpredominates in at least one class of the monomers characterizing theblocks defined hereinbefore. For example, blocks A may comprisestyrene/alpha-methylstyrene copolymer blocks or styrene/butadiene randomor tapered copolymer blocks as long as the blocks individuallypredominate in alkenyl arenes. The A blocks are preferably monoalkenylarene. The term "monoalkenyl arene" will be taken to includeparticularly those of the benzene series such as styrene and its analogsand homologs including o-methylstyrene, p-methylstyrene,p-tert-butylstyrene, 1,3-dimethylstyrene, alpha-methylstyrene and otherring alkylated styrenes, particularly ring-methylated styrenes, andother monoalkenyl polycyclic aromatic compounds such as vinylnaphthalene, vinyl anthracene and the like. The preferred monoalkenylarenes are monovinyl monocyclic arenes such as styrene andalpha-methylstyrene, and styrene is particularly preferred.

The blocks B may comprise homopolymers of conjugated diene monomers,copolymers of two or more conjugated dienes, and copolymers of one ofthe dienes with a monoalkenyl arene as long as the blocks B predominatein conjugated diene units. The conjugated dienes are preferably onescontaining from 4 to 8 carbon atoms. Examples of such suitableconjugated diene monomers include: 1,3-butadiene (butadiene),2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene,1,3-pentadiene (piperylene), 1,3-hexadiene, and the like. Mixtures ofsuch conjugated dienes may also be used. The preferred conjugated dienesare butadiene and isoprene.

Preferably, the block copolymers of conjugated dienes and alkenyl arenehydrocarbons which may be utilized include any of those which are low inmodulus relative to the respective polyester, preferably less than 1:10(ratio of tensile modulus of block copolymer to tensile modulus ofpolyester) and those butadiene derived elastomers which have1,2-microstructure contents prior to hydrogenation of from about 7 toabout 100 percent, preferably from about 25 to about 65 percent, morepreferably from about 35 to about 55 percent. Such block copolymers maycontain various ratios of conjugated dienes to alkenyl arenes. Theproportion of the alkenyl arene blocks is between about 1 and about 99percent by weight of the multiblock copolymer, preferably between about2 and about 60 percent, more preferably between about 2 and about 55percent by weight and particularly preferable between about 2 and about40 percent by weight. When the alkenyl arene content is not more thanabout 60 percent by weight, preferably not more than about 55 percent byweight, the precursor block copolymer has characteristics as a rubbery(soft) polymer; and when the alkenyl arene content is greater than about60 percent by weight, preferably more than about 70 percent by weight,the precursor block copolymer has characteristics as a resinous polymer.

The average molecular weights of the individual blocks may vary withincertain limits. In most instances, the monoalkenyl arene blocks willhave average molecular weights in the order of about 1,000 to about125,000, preferably about 1,000 to about 60,000, while the conjugateddiene blocks either before or after hydrogenation will have averagemolecular weights in the order of about 10,000 to about 450,000,preferably about 10,000 to about 150,000. The total average molecularweight of the multiblock copolymer is typically in the order of about12,000 to about 700,000, preferably from about 12,000 to about 270,000.These molecular weights are most accurately determined by gel permeationchromatography.

The block copolymers may be produced by any well known blockpolymerization or copolymerization procedures including the well knownsequential addition of monomer techniques, incremental addition ofmonomer technique or coupling technique as illustrated in, for example,U.S. Pat. Nos. 3,251,905; 3,390,207; 3,598,887 and 4,219,627, thedisclosures of which are incorporated herein by reference. As is wellknown in the block copolymer art, tapered copolymer blocks can beincorporated in the multiblock copolymer by copolymerizing a mixture ofconjugated diene and alkenyl arene monomers utilizing the difference intheir copolymerization reactivity rates. Various patents describe thepreparation of multiblock copolymers containing tapered copolymer blocksincluding U.S. Pat. Nos. 3,251,905; 3,265,765; 3,639,521 and 4,208,356,the disclosures of which are incorporated herein by reference.

It should be observed that the above-described polymers and copolymersmay, if desired, be readily prepared by the methods set forth above.However, since many of these polymers and copolymers are commerciallyavailable, it is usually preferred to employ the commercially availablepolymer as this serves to reduce the number of processing steps involvedin the overall process.

These polymers and copolymers are preferably hydrogenated to increasetheir thermal stability and resistance to oxidation. The hydrogenationof these polymers and copolymers may be carried out by a variety of wellestablished processes including hydrogenation in the presence of suchcatalysts as Raney Nickel, noble metals such as platinum, palladium andthe like, and soluble transition metal catalysts. Suitable hydrogenationprocesses which can be used are ones wherein the diene-containingpolymer or copolymer is dissolved in an inert hydrocarbon diluent suchas cyclohexane and hydrogenated by reaction with hydrogen in thepresence of a soluble hydrogenation catalyst. Such processes aredisclosed in U.S. Pat. Nos. 3,113,986 and 4,226,952, the disclosures ofwhich are incorporated herein by reference. The polymers and copolymersare hydrogenated in such a manner as to produce hydrogenated polymersand copolymers having a residual ethylenic unsaturation content in thepolydiene block of not more than about 20 percent, preferably not morethan about 10 percent, most preferably not more than about 5 percent, oftheir original ethylenic unsaturation content prior to hydrogenation.

Modified Block Copolymers

The modified block copolymers according to the present invention arepreferably grafted or substituted in the alkenyl arene block by themetalation process as later described herein. Exemplary reactions aregiven below, utilizing an exemplary styrene unit from a polystyrenesegment of a suitable block copolymer: ##STR4## where: RLi=Alkyl Lithium##STR5##

The structure of the substituted block copolymer specifically determinedby locating the functionality on the alkenyl arene block gives the blockcopolymer a substantially greater degree of thermal stability.

Graftable Compounds

In general, any materials having the ability to react with the metalatedbase polymer are operable for the purpose of this invention.

In order to incorporate functional groups into the metalated basepolymer, electrophiles capable of reacting with the metalated basepolymer are necessary. Reactants may be polymerizable ornonpolymerizable; however, preferred electrophiles are nonpolymerizablewhen reacted with metalated polymers such as those utilized herein.

The class of preferred electrophiles which will form graft polymerswithin the scope of the present invention include reactants from thefollowing groups carbon dioxide, ethylene oxide, aldehydes, ketones,carboxylic acid derivatives such as their salts, esters and halides,epoxides, sulfur, boron alkoxides, isocyanates and various siliconcompounds.

These electrophiles may contain appended functional groups as in thecase of N,N-dimethyl-p-aminobenzaldehyde where the amine is an appendedfunctional group and the aldehyde is the reactive electrophile.Alternatively, the electrophile may react to become the functional siteitself; as an example, carbon dioxide (electrophile) reacts with themetalated polymer to form a carboxyl functional group. By these routes,polymers could be prepared containing grafted sites selected from one ormore of the following groups of functionality type carboxylic acids,their salts and esters, ketones, alcohols and alkoxides, amines, amides,thiols, borates, anhydrides, and functional groups containing a siliconatom.

These functionalities can be subsequently reacted with other modifyingmaterials to ultimately produce carboxyl functional groups appendedthereon which are necessary for the impact modification effect observedand relied upon herein. In some cases, the reaction could take placesimultaneously with the grafting process but in most examples it wouldbe practiced in subsequent post modification reaction. The graftedcarboxyl functional groups may be present as carboxylic acids, theirsalts and esters, and combinations thereof. Additionally, carboxylfunctional groups in any of these forms may be further reacted withother modifying materials to convert from one form to another, therebyvarying the relative proportions of each of these carboxylate forms tothe others. For example, grafted carboxylic acid groups could besuitably modified by esterifying same by appropriate reaction withhydroxy-containing compounds of varying carbon atom lengths.

The effective amount of carboxyl functional groups for toughening thecomposition is on the average at least about one (1), preferably atleast about ten (10), carboxyl functional groups per molecule of theblock copolymer. It is presently believed that the addition of about one(1) electrophile per aromatic ring of the A blocks is limiting. Thus, ifcarbon dioxide is used as the electrophile, this translates to about one(1) carboxyl group per aromatic ring. Therefore, the effective amount ofcarboxyl functional groups corresponds to from about an average of onecarboxyl functional group per molecule of the block copolymer to aboutan average of one carboxyl functional group per aromatic ring of the Ablock, respectively. Preferably, the functionality level is on theaverage from about ten carboxyl functional groups per molecule of thecopolymer to about one carboxyl functional group per aromatic ring ofthe A block, and, more preferably, on the average from about tencarboxyl functional groups per molecule of the copolymer to about onecarboxyl functional group per every two aromatic rings of the A block;and, yet more preferably, on the average from about ten carboxylfunctional groups per molecule of the copolymer to about one carboxylfunctional group per every ten aromatic rings of the A block. Aspreviously noted, it is currently believed that the average of oneaddition per aromatic ring is limiting. However, it still remains thatthe greater the degree of functionality (carboxyl group content)attained, the greater the improvement in impact properties.

Neutralization of Modified Block Copolymer

The carboxylic acid groups in the modified block copolymers of thepresent invention may then be "neutralized" by reacting the polymer withan ionizable metal compound to obtain a metal salt. The improvement inimpact properties resulting from the blend of the polyester and thecarboxylated block copolymer is greatly influenced by the type ofpolyester, by the degree of carboxyl functionalization in the blockcopolymer, and by the degree of neutralization thereof. For example, toobtain an optimum in the impact properties of a PET blend at aparticular functionality level, the carboxylated block copolymer ispreferably in the all acid form. On the other hand, to obtain an optimumin the impact properties of a PBT blend at a particular functionalitylevel, the carboxylated block copolymer is preferably partiallyneutralized.

The metal ions which are suitable in forming the neutralized blockcopolymers of the present invention are mono-, di- and trivalent ions ofmetals in Groups IA, IB, IIA, IIB, IIIA, IIIB, IV and VIII, of thePeriodic Table of Elements. These metal ions can be used alone or in anymixture thereof. Suitable monovalent metal ions are Na⁺, K⁺, Li⁺, Cs⁺,Ag⁺, Hg⁺ and Cu⁺. Suitable divalent metal ions are Mg⁺², Ca⁺², Sr⁺²,Ba⁺², Cu⁺², Cd⁺², Hg⁺², Sn⁺², Pb⁺², Fe⁺², Co⁺², Ni⁺² and Zn⁺². Suitabletrivalent metal ions are Al⁺³, Sc⁺³, Fe⁺³, La⁺³ and Y⁺³. Preferablemetal containing compounds for neutralization of the carboxylated blockcopolymers herein are hydroxides, oxides, alcoholates, carboxylates,formates, acetates, methoxides, ethoxides, nitrites, carbonates andbicarbonates of the above-referenced metal ions.

The degree of carboxyl functionality and of neutralization may bemeasured by several techniques. For example, infrared analysis may beemployed to determine the overall degree of functionality calculatedfrom the changes resulting in the absorption bands associated with--COOH units. Additionally, the titration of a solution of the blockcopolymer with a strong base may be utilized to determine the degree offunctionality and/or degree of neutralization (metal carboxylate saltcontent.) Neutralization as used herein is based on the percentage ofcarboxylate ions (--COO⁻) as compared to the total carboxyl groupfunctionality, i.e., carboxylic acid plus the carboxylate ions.

In general, it was found that the added metal ion reacts approximatelystoichiometrically with the carboxyl functional groups (acid form) inthe polymer up to about 80 percent neutralization. Thereafter, excessquantities of the metal compound are necessary to carry theneutralization to completion.

Thus, each of these carboxyl functional groups may be either in thecarboxylic acid or ester form or ionized by neutralization with metalions having a positive ionized valence state. For example, from 100percent to 0 percent of the carboxyl functional groups may be in theacid form (--COOH); and, correspondingly, from 0 percent to 100 percentof the carboxyl functional groups may be in the salt form (neutralized,e.g. --COOLi).

Preparation of the Modified Block Copolymers

The polymers may be prepared by any convenient manner. Preferably, thepolymer is prepared such that the functional groups are incorporatedinto the block copolymer primarily on the aromatic portion of thealkenyl arene block via metalation.

Metalation may be carried out by means of a complex formed by thecombination of a lithium component which can be represented byR'(Li)_(x) with a polar metalation promoter. The polar compound and thelithium component can be added separately or can be premixed orpre-reacted to form an adduct prior to addition to the solution of thehydrogenated copolymer. In the compounds represented by R'(Li)_(x), theR' is usually a saturated hydrocarbon radical of any length whatsoever,but ordinarily containing up to 20 carbon atoms, and may also be asaturated cyclic hydrocarbon radical of e.g. 5 to 7 carbon atoms. In theformula R'(Li)_(x), x is an integer of 1 to 3. Representative speciesinclude, for example: methyllithium, isopropyllithium, sec-butyllithium,n-butyllithium, t-butyllithium, n-dodecyllithium, 1,4-dilithiobutane,1,3,5-trilithiopentane, and the like. The lithium alkyls must be morebasic than the product, metalated polymer alkyl. Of course, other alkalimetal or alkaline earth metal alkyls may also be used; however, thelithium alkyls are presently preferred due to their ready commercialavailability. In a similar way, metal hydrides may also be employed asthe metalation reagent but the hydrides have only limited solubility inthe appropriate solvents. Therefore, the metal alkyls are preferred fortheir greater solubility which makes them easier to process.

Lithium compounds alone usually metalate copolymers containing aromaticand olefinic functional groups with considerable difficulty and underhigh temperatures which may tend to degrade the copolymer. However, inthe presence of tertiary diamines and bridgehead monoamines, metalationproceeds rapidly and smoothly.

Generally, the lithium metalates the position allylic to the doublebonds in an unsaturated polymer. In the metalation of polymers in whichthere are both olefinic and aromatic groups, the metalation will occurin the position in which metalation occurs most readily, as in positions(1) allylic to the double bond (2) at a carbon to which an aromatic isattached, (3) on an aromatic group, or (4) in more than one of thesepositions. In the metalation of saturated polymers having aromaticgroups as is preferably the case herein, the metalation will occurprimarily on an aromatic group and as a minor product at a carbon towhich an aromatic is attached. In any event, it has been shown that avery large number of lithium atoms are positioned variously along thepolymer chain, attached to internal carbon atoms away from the polymerterminal carbon atoms, either along the backbone of the polymer or ongroups pendant therefrom, or both, in a manner depending upon thedistribution of reactive or lithiatable positions. This distinguishesthe lithiated copolymer from simple terminally reactive polymersprepared by using a lithium or even a polylithium initiator inpolymerization thus limiting the number and the location of thepositions available for subsequent attachment. With the metalationprocedure described herein, the extent of the lithiation will dependupon the amount of metalating agent used and/or the groups available formetalation. The use of a more basic lithium alkyl such astert-butyllithium alkyl may not require the use of a polar metalationpromoter.

The polar compound promoters include a variety of tertiary amines,bridgehead amines, ethers, and metal alkoxides.

The tertiary amines useful in the metalation step have three saturatedaliphatic hydrocarbon groups attached to each nitrogen and include, forexample:

(a) Chelating tertiary diamines, preferably those of the formula R₂N--CH₂ --_(y) NR₂ in which each R can be the same or different,straight- or branched-chain alkyl group of any chain length containingup to 20 carbon atoms, or more, all of which are included herein and ycan be any whole number from 2 to 10, and particularly the ethylenediamines in which all alkyl substituents are the same. These include,for example: tetramethylethylenediamine, tetraethylethylenediamine,tetradecylenediamine, tetraoctylhexylenediamine, tetra-(mixed alkyl)ethylene diamines, and the like.

(b) Cyclic diamines can be used, such as, for example, theN,N,N',N'-tetraalkyl 1,2-diamino cyclohexanes, the N,N,N',N'-tetraalkyl1,4-diamino cyclohexanes, N,N'-dimethylpiperazine, and the like.

(c) The useful bridgehead diamines include, for example, sparteine,triethylenediamine and the like.

Tertiary monoamines such as triethylamine are generally not as effectivein the lithiation reaction. However, bridgehead monoamines such as1-azabicyclo[2.2.2] octane and its substituted homologs are effective.

Ethers and the alkali metal alkoxides are presently less preferred thanthe chelating amines as activators for the metalation reaction due tosomewhat lower levels of incorporation of functional group containingcompounds onto the copolymer backbone in the subsequent graftingreaction.

In general, it is most desirable to carry out the lithiation reaction inan inert solvent such as saturated hydrocarbons. Aromatic solvents suchas benzene are lithiatable and may interfere with the desired lithiationof the hydrogenated copolymer. The solvent/copolymer weight ratio whichis convenient generally is in the range of about 5:1 to about 20:1.Solvents such as chlorinated hydrocarbons, ketones, and alcohols, shouldnot be used because they destroy the lithiating compound.

Polar metalation promotors may be present in an amount sufficient toenable metalation to occur, e.g. amounts between about 0.01 and about100 or more preferably between about 0.1 to about 10 equivalents perequivalent of lithium alkyl.

The equivalents of lithium employed for the desired amount of lithiationgenerally range from such as about 0.001 to about 3.0 per alkenyl arenehydrocarbon unit in the copolymer, presently preferably about 0.01 toabout 1.0 equivalents per alkenyl arene hydrocarbon unit in thecopolymer to be modified. The molar ratio of active lithium to the polarpromoter can vary from such as about 0.01 to about 10.0. A preferredratio is about 0.5 to about 2.0.

The amount of lithium alkyl employed can be expressed in terms of thelithium alkyl to alkenyl arene hydrocarbon molar ratio. This ratio mayrange from a value of 1 (one lithium alkyl per alkenyl arene hydrocarbonunit) to as low as 1×10⁻³ (1 lithium alkyl per 1000 alkenyl arenehydrocarbon units).

The process of lithiation can be carried out at temperatures in therange of such as about -70° C. to about +150° C., presently preferablyin the range of about 25° C. to about 75° C., the upper temperaturesbeing limited by the thermal stability of the lithium compounds. Thelower temperatures are limited by considerations of production cost, therate of reaction becoming unreasonably slow at low temperatures. Thelength of time necessary to complete the lithiation and subsequentreactions is largely dependent upon mixing conditions and temperature.Generally, the time can range from a few seconds to about 72 hours,presently preferably from about 1 minute to about 1 hour.

Grafting Step

The next step in the process of preparing the modified block copolymeris the treatment of the lithiated hydrogenated copolymer, in solution,without quenching in any manner which would destroy the lithium sites,with a species capable of reacting with a lithium anion. These speciesare selected from the class of molecules called electrophiles and mustcontain functional groups capable of undergoing nucleophilic attack by alithium anion. As such, the modified block copolymer herein is thereaction product of an electrophile with an activated base (unmodifiedhydrogenated) block copolymer primarily at lithium anion sites on thearomatic substrates thereof, as opposed to the reaction product of anelectrophile (strong Lewis acid) with an unactivated base blockcopolymer on the aromatic substrates thereof.

Such species will react to give polymer bound functional groupsincluding but not limited to:

    ______________________________________                                         ##STR6##                                                                              carboxyl  CNR.sub.2  Amine                                           COH      hydroxyl                                                                                 ##STR7##  Amide                                           COR      ether     SH         Thiol                                            ##STR8##                                                                              ketone    B(OR).sub.2                                                                              Borane Containing                                ##STR9##                                                                              aldehyde                                                                                 ##STR10## Silicon Containing                              ______________________________________                                    

If necessary, the process also includes further chemistry on themodified block copolymer to carboxylate same. The resulting carboxylfunctional groups may then be easily converted from or to a carboxylicacid form or a neutralized metal carboxylate salt form. Whether the allacid or partially neutralized form is preferable to produce the greatestimprovement in impact properties is dependent upon the polyester chosenfor the blend. A simple Notched Izod toughness test (ASTM-256) on a testspecimen (bar) molded from such blends is clearly indicative and withinthe skills possessed by one of ordinary skill in the art.

The desired degree of neutralization may be achieved by various methods.If the modified block copolymer is in an all acid form or in a partiallyneutralized form and additional neutralization is desired,neutralization is preferably carried out under conditions which allowfor a homogeneous uniform distribution of the metal containing compoundin the modified block copolymer. No particular reaction conditions areessential except that the conditions should preferably permit theremoval of the neutralization product. More specifically, theneutralization reaction is preferably carried either (1) by adding themetal containing compound, directly or in solution, to a solution of themodified block copolymer and then, on neutralization, precipitating andseparating the resulting polymer; or (2) by melt blending the blockcopolymer with the metal containing compound. The melt blending ispreferably conducted at elevated temperatures to facilitate homogeneousdistribution of the metal containing compound and to volatilize theneutralization product.

Alternatively, if the modified block copolymer is in an all neutralizedsalt form or in a partially neutralized form and additionalacidification (i.e., reverse-neutralization) is desired, acidificationis likewise preferably carried out under conditions which allow for ahomogeneous uniform distribution of the acid in the modified blockcopolymer. The acid utilized is preferably an organic acid, for exampleacetic acid or citric acid. The resulting metal-salt acidificationproduct may be harmful to the resulting modified block copolymer orblend incorporating same. Therefore, the metal salt may be removed byconventional means if so desired.

As an additional alternative, the all acid and the all neutralized saltforms of the block copolymer may be blended with each other or togetherwith the desired polyester or polyesters by either the solution or meltblending method mentioned above, to achieve the desired degree ofneutralization. It is to be understood, however, that the specifictechnique employed is not critical as long as it meets the requirementsset forth above. The extent of the neutralization i.e., the degree towhich the metal ion is linked with the carboxylate ion may be readilyanalyzed by titration methods.

It is not essential that the metal containing compound be added as such,but it is possible to form the metal containing compound in situ fromcomponents which react with each other in the desired manner in thepolymer environment. Thus, it is possible to add a metal oxide to theall acid or partially neutralized block copolymer then add an acid suchas acetic acid in the proper proportion and form the metal containingcompound, i.e., the metal acetate, while the polymer is milled. Themetal containing compound then neutralizes the block copolymer to thedesired degree depending on the proportion of metal containing compoundformed.

Preparation of the Final Compositions

The toughened thermoplastic polymer compositions of the presentinvention can be readily prepared by using any conventional mixingapparatus which is normally used for mixing or blending of polymersubstances. Examples of such apparatus are single or multiple screwextruders, mixing rollers, Brabender, Banbury mills, kneaders and thelike. Alternatively, the blends may be made by coprecipitation fromsolution, blending or by dry mixing together of the components, followedby melt fabrication of the dry mixture by extrusion.

The polyester blends of the present invention may be prepared bymelt-blending the desired proportion of polyester, ranging from about 50percent to about 99 percent, with the desired proportion of the modifiedblock copolymer, ranging from about 1 percent to about 50 percent.Taking economic and commercial considerations into account, theproportion of polyester preferably ranges from about 70 percent to about95 percent, or most preferably ranges from about 70 percent to about 90percent, with the modified block copolymer making up the difference inthe polyester/block copolymer blend.

The impact properties of the blends of this invention are improved ascharacterized by a higher notched Izod value over the polyester alone orin a blend with the base (unmodified hydrogenated) copolymer. The amountof functionality and the quantity of ions employed in the compositionwill differ with the degree of impact properties desired. The degree ofneutralization effective in imparting improved impact properties to themodified block copolymer/polyester blend ranges from about 0 to about100 percent of the carboxyl groups in the modified block copolymer.Within this range, blends considered to be "super-tough" may beattained. A blend is considered to be "super-tough" herein when its 1/8"Notched Izod at room temperature in excess of 10 ft-lb/in and the blendexperiences ductile failure, as opposed to brittle failure.

The improvement in toughness of the compositions herein is related tothe amount of adherent sites in the modified block copolymer componentand the degree of block copolymer dispersion. The blends of the presentinvention are unlike the interpenetrating networks formed by the binarypolyester/unmodified block copolymer blends of Gergen et al. in U.S.Pat. No. 4,101,605. Gergen et al. utilized selective extraction toestablish the presence or absence of the interlocking nature andcontinuity of each of the components therein. Similar selectiveextraction experiments were performed on molded or extruded testspecimens made from blends of the present invention and from blends ofunmodified block copolymers with polyester. The unmodified blockcopolymer in the test specimens herein coexisted as an interpenetratingnetwork with the polyester as evidenced by the retention of shape by inthe injection molded bars when placed in a polyester solvent, such ashot o-cresol, trifluroacetic acid or o-chlorophenol. However, when thetest specimens utilizing the blends of the present invention were placedin the polyester solvent, the test specimens disintegrated (lost allshape and form) in a facile manner leaving particles of the modifiedblock copolymer. The foregoing indicates that the modified blockcopolymer in the test specimens herein coexisted as a dispersed phasewithin the polyester. However, it is believed that as the amounts ofpolyester and the modified block copolymer become relatively equal (sayabout 50:50 to about 60:40 respectively) partially continuousinterlocking networks may be formed.

The mechanism of adhesion and the role of the copolymer/polyesterinterface to promote block copolymer phase size reduction is notentirely understood. However, it appears that the strong interaction orpotential grafting reaction between same and block copolymer phase sizeare interrelated. To some extent, enhancing the extent of interaction orreaction appears to facilitate a reduction in block copolymer phasesize. Moreover, it appears that by increasing the blockcopolymer/polyester interface more sites are made available for theunknown mechanism herein to operate upon. However, whether the blockcopolymer may be continuous, partially continuous, or dispersed withinthe polyester, optimum toughening of the respective polyester issurprisingly not achieved at the smallest attainable phase size. Below acertain phase size, super-toughened polyester blend properties are notattained. For example, when the minimum amount of carboxyl functionalgroups required for super-toughening are present, super-toughened PBTblends are obtained when the modified block copolymer phase size is fromabout 0.4μ to about 0.7μ. The phase size required for super-roughenedPET blends is from about 0.2μ to about 0.5μ.

The polymer compositions of the present invention can further containother conventional additives. Examples of such additives are reinforcingmaterials such as silica, carbon black, clay, glass fibers, organicfibers, calcium carbonate and the like, as well as stabilizers andinhibitors of oxidative, thermal, and ultraviolet light degradation,lubricants and mold release agents, colorants including dyes andpigments, nucleating agents, fire retardants, plasticizers, etc.

The stabilizers can be incorporated into the composition at any stage inthe preparation of the thermoplastic composition. Preferably, thestabilizers are included early to preclude the initiation of degradationbefore the composition can be protected. Such stabilizers must becompatible with the composition.

The compositions of the present invention can be readily molded orformed into various kinds of useful articles by using any conventionalmolding, injection molding, blow molding, pressure forming, rotationalmolding and the like. Examples of the articles are sheets, films, foamedproducts as well as injection-molded articles, blow-molded articles,pressure-formed articles and rotational-molded articles having variouskinds of shapes. These articles can be used in the fields of, forexample, automobile parts, electrical parts, mechanical parts, packagingmaterials, building materials and the like.

To assist those skilled in the art in the practice of this invention,the following Examples are set forth as illustrations. It is to beunderstood that in the specification and claims herein, unless otherwiseindicated, when the amount of the polyester or block copolymer isexpressed in terms of percent by weight, it is meant percent by weightbased on the total amount of these materials which is employed in themelt-blending. Furthermore, it is to be understood that, unlessotherwise indicated, when the amount of carboxylic acid (--COOH) orcarboxylate ion (--COO⁻) is expressed in terms of percent by weight (%w), it is meant percent by weight based on the corresponding base blockcopolymer. It is to be further understood that the carboxylate salt tocarboxylic acid ratio (salt to acid ratio) is equal to (the numericalvalue of % neutralization): (100 minus the numerical value of %neutralization). In these Examples, injection molded bars of thesecompositions were tested using the following test procedures in thedry-as-molded state:

Notched Izod toughness: at each end ASTM D-256

Flexural Modulus: ASTM D-790

Properties represent an average of at least five test specimens.

EXAMPLES OF THE INVENTION

Having thus broadly described the present invention, it is believed thatthe same will become even more apparent by reference to the followingexamples. It will be appreciated, however, that the examples arepresented solely for the purposes of illustration and should not beconstrued as limiting the invention.

The base (unmodified hydrogenated) block copolymers used were thepolystyrene-poly(ethylene/propylene) (S-EP) andpolystyrene-poly(ethylene/butylene)-polystyrene (S-EB-S) blockcopolymers shown in Table 1. The base block copolymers were the productsof selectively hydrogenating a polystyrene-polyisoprene (S-I) orpolystyrene-polybutadiene-polystyrene (S-B-S) block copolymers(precursor block copolymers) effected by use of a catalyst comprisingthe reaction products of an aluminum alkyl compound with nickelcarboxylates. The base block copolymers have a residual ethylenicunsaturation of less than about 2% of the original unsaturation in thepoly(conjugated diene) block and have a residual aromatic unsaturationof greater than 95% of the original unsaturation in the polystyreneblock.

                                      TABLE 1                                     __________________________________________________________________________               Block                                                              Base  Styrene                                                                            Styrene                                                            Block Content                                                                            Content                                                                            Total                                                                              Polymer Structure and                                    Copolymer                                                                           (wt. %)                                                                            (wt. %)                                                                            Mw.  Block Mw                                                 __________________________________________________________________________    A     29   29   66,000                                                                             9,600-46,800-9,600                                                                       (S-EB-S)                                      B     32   32   181,000                                                                            29,000-123,000-29,000                                                                    (S-EB-S)                                      C     29   29   49,700                                                                             7,200-35,300-7,200                                                                       (S-EB-S)                                      D     30   30   51,500                                                                             7,700-36,100-7,700                                                                       (S-EB-S)                                      E     28   28   159,000                                                                            44,600-114,400                                                                           (S-EP)                                        F     38   38   98,100                                                                             37,200-60,900                                                                            (S-EP)                                        __________________________________________________________________________     Remarks:                                                                      S  Polymer block composed chiefly of styrene.                                 EB  Polymer block composed chiefly of hydrogenated polybutadiene and          referred to as ethylene/butylene.                                             EP  Polymer block composed chiefly of hydrogenated polyisoprene and           referred to as ethylene/propylene.                                            Mw  Weight average molecular weight.                                     

Per the following examples, the base block copolymer was first modifiedto varying degrees of carboxyl group functionality (content) by graftingcarboxyl groups onto the polystyrene blocks via the metalation processdescribed herein. The modified block copolymers were then furthermodified with lithium, sodium and zinc metals to form carboxylate saltsat various acid to carboxylate salt contents (degree of neutralization).

EXAMPLE 1 Modified Block Copolymer (Method I)

In this experiment, a modified block copolymer "G" was preparedutilizing the base block copolymer "A". 2270 gm of polymer "A" weredissolved in 15 gallons of cyclohexane. This mixture was placed in a 20gallon stainless steel pressurized reaction vessel and pressurized toabout 25 psig. 0.8 meq/gm polymer of tetramethylethylene diamine wasthen added to the vessel. A small amount, 0.5 ml, of 1-1diphenylethylene (an indicator) was then added to the reactor.Sec-butyllithium was then added incrementally until a yellow color wasobtained, indicating the absence of impurities.

The reactor contents were then heated to 60° C. Next, 0.4 meq/gm polymerof additional sec-butyllithium was added to the reactor. After 21/2hours reaction time, the contents of the vessel were transferred toanother vessel which contained a stirring mechanism. The second vesselcontained 2-3 lbs of dry ice (solid CO₂), 10 gallons of tetrahydrofuran,and 5 gallons of diethylether. The solution was stirred for 30 minutes.Next, 85 grams of acetic acid in an isopropanol solution was added tothe reactor. This solution was stirred for 16 hours. The modified blockcopolymer was then recovered by steam stripping.

Infrared analysis of the polymer showed the presence of both boundcarboxylic acid at 1690 cm⁻¹ and bound lithium carboxylate salt at1560-1600 cm⁻¹. By colorimetric titration with 0.01N KOH in methanolusing a phenothalein indicator, it was found that the level of boundacid was 0.3 wt % COOH. After repeated washings of the polymer withalcoholic hydrochloric acid (reacidification), infrared showed thatcomplete conversion of salt to acid took place. Alternatively, thepolymer may be redissolved in THF and then adding an excess of aceticacid (reacidification) to convert the salt to carboxylic acid groups.Thereafter, the polymer may be coagulated in methanol. Titration of thewashed polymer gave a bound acid level of 0.4% w COOH. Thus, thecarboxyl functionality of Polymer "G" is 0.4% w. Prior toreacidification, the polymer contained 0.3% w --COOH and 0.1% --COOLi(lithium carboxylate salt).

Polymers H, J, K and L (see Table 2) were prepared using a modificationof the procedure described for the preparation of Polymer G. Polymer Hused Polymer B as a starting material. Polymers J, K and L used PolymerC as a starting material. Polymer J was recovered by precipitation inisopropyl alcohol, as opposed to steam coagulation like the otherpolymers herein. These preparations respectively employed a decreased orincreased amount of the metalation reagent (promoter) relative to theamount of polymer substrate to achieve the carboxylate contents shown inTable 2.

EXAMPLE 2 Modified Block Copolymer (Method II, Preferred)

In this experiment, a modified block copolymer "N" was preparedutilizing the base block copolymer "D". A 5% (wt/wt) solution of PolymerD (see Table 1) in cyclohexane (3100 lb) was treated, in a closed vesselunder nitrogen, with the metalation promoter,N,N,N',N'-tetramethylethylenediamine (TMEDA) (14 lb, 55 mol) and atitration indicator, 1,1-diphenylethylene (21 g, 0.1 mol). This solutionwas heated with stirring to 50° C. and titrated with s-butyllithiumsolution to remove impurities. At the endpoint of the titration, aslight excess of s-butyllithium reagent was reacted with the indicatorforming a benzylic anion which gave the solution a yellow/orange color;the persistence of this color was taken as an indication that thesolution was now anhydrous and anaerobic. These conditions weremaintained throughout the rest of the experiment.

The metalation reagent, s-butyllithium (41 lb of a 12% (wt/wt) solutionin cyclohexane, 35 mol), was added to the reaction mixture over a periodof 15 minutes. The lithiated polymer cement was quite viscous and yellowin color. An aliquot of the cement was removed and treated with anexcess of D₂ O. This procedure placed a deuterium atom on the polymer atsites which had been lithiated. Analysis of the deuterated polymer usinga Deuterium NMR technique found 89% of the deuterium was attached to thearomatic ring. Appropriate control experiments showed that the remainderof the deuterium label was at benzylic centers (about 5%) in thepolystyrene segment and at allylic centers (about 6%) in the rubber ofthe polymer. These results showed that the polymer was lithiatedprincipally in the styrene blocks (at least 94%).

After 1 hour in the lithiation reactor (60° C.), the cement wastransferred to a closed vessel containing carbonated (142 lb of CO₂,1500 mol) tetrahydrofuran (THF) (about 380 gal). The lithiated polymercement was introduced below the surface of the CO₂ /THF mixture. Whilecarboxylation was likely instantaneous, the mixture was stirred at roomtemperature for 4 hr. The reactor product was acidified by the additionof 26 lbs. of acetic acid (200 mol). Modified block copolymer N wasrecovered by steam coagulation and dried at 50°-60° C. in a vacuum oven.

To measure the polymer bound carboxylic acid (--COOH) content of PolymerN, an aliquot of the finished polymer was dissolved in THF and titratedto a phenolphthalein endpoint using 0.01N KOH in methanol. The titrationfound 1.15% wt --COOH.

To determine the total carboxylate content, both --COO⁻ and --COOHmoieties of Polymer N, an aliquot of the finished polymer was dissolvedin cyclohexane at a 10% solids level and treated with an equal volume ofacetic acid. Control experiments had shown that the acid treatmentconverted polymer bound --COO⁻ to --COOH species. The acidified mixturewas repeatedly washed with H₂ O until the wash sample was neutral toremove excess acetic acid and acetate salts. The fully acidified polymerwas precipitated in isopropanol, dried and titrated as outlined above.The titration found 1.15% wt --COOH; the same result as had beenobserved for the as finished polymer. By difference, we concluded thatthe as finished product, Polymer N, contained no carboxylate salt;Polymer N was in the all acid form --COOH.

An infrared analysis based upon characteristic IR bands for the --COOHspecies (1690 cm⁻¹) and polystyrene (1590 cm⁻¹) (in essence an internalstandard signal) corroborated the titration results. The IR data werefrom a solution cast film of Polymer N.

Polymers M, P, Q, R, S, and T (see Table 2) were prepared using amodification of the procedure described for the preparation of PolymerN. Polymers M, P, Q, R, S, and T were prepared on a 5 lb Polymer M and Pused Polymer D as a starting material. Polymers Q, R and S used PolymerE as a starting material. Polymer T used Polymer F as a startingmaterial. These preparations respectively employed a decreased and anincreased amount of the metalation reagent (promoter) relative to theamount of polymer substrate. This led to products having lower andhigher carboxylate contents, respectively.

                                      TABLE 2                                     __________________________________________________________________________    Modified                                                                            Base  Carboxyl                                                                              Ratio of Carboxyl Groups                                                                   Carboxyl Groups                              Block Block Functionality                                                                         to Alkenyl Arene Units in                                                                  per Molecule of                              Copolymer                                                                           Copolymer                                                                           (% w-COOH)                                                                            Base Block Copolymer                                                                       Block Copolymer                              __________________________________________________________________________    G     A     0.40    1:33.4        5.9                                         H     B     0.33    1:43.7       13.3                                         J     C     0.22    1:59.3        2.4                                         K     C     1.18    1:11.1       13.0                                         L     C     1.39    1:9.4        15.4                                         M     D     1.00    1:13.5       11.4                                         N     D     1.15    1:11.6       13.2                                         P     D     1.40    1:9.6        16.0                                         Q     E     0.1     1:126         3.5                                         R     E     0.5     1:24.2       17.7                                         S     E     1.3     1:9.7        45.9                                         T     F     2.6     1:6.6        56.7                                         __________________________________________________________________________

EXAMPLE 3 Neutralized Modified Block Copolymers

In this example, modified block copolymers were neutralized utilizingmonovalent metal counterions, such as sodium (Na¹⁺) and lithium (Li¹⁺),and divalent metal counterions, such as zinc (Zn²⁺). The modified blockcopolymers were obtained by adding aqueous sodium hydroxide, lithiumhydroxide and zinc acetate solutions in THF, respectively, to themodified block copolymer (all acid). The modified block copolymersneutralized utilizing magnesium metal counterions may be obtained byneutralizing the respective modified block copolymer (all acid) withmagnesium methoxide in anhydrous methanol. For those neutralizedmodified block copolymers having a metal carboxylate salt contentgreater than 80% based on total carboxyl groups, an excess of the metalcarrying compound was utilized (typically five times stoichiometric) toensure the high degree of neutralization.

Table 3 indicates the various neutralized block copolymers produced fromthe corresponding modified block copolymers for purposes of thefollowing examples.

                  TABLE 3                                                         ______________________________________                                                                     %                                                Modified                                                                              Carboxyl             Carboxyl                                         Block   Functionality                                                                            Metal     Groups  % w  % w                                 Copolymer                                                                             (% w)      Counterion                                                                              Neutralized                                                                           Acid Salt                                ______________________________________                                        G       0.40       --        0       0.40 --                                  U1      0.40       Li        25      0.30 0.10                                U2      0.40       Li        100     --   0.40                                H       0.22       --        0       0.22 --                                  V1      0.22       Li        55      0.10 0.12                                V2      0.22       Li        100     --   0.22                                J       0.33       --        0       0.33 --                                  W1      0.33       Li        33      0.22 0.11                                K       1.18       --        0       1.18 --                                  X1      1.18       Li        49      0.60 0.58                                L       1.39       --        0       1.39 --                                  Y1      1.39       Li        19      1.12 0.27                                Y2      1.39       Li        100     --   1.39                                M       1.00       --        0       1.00 --                                  Z1      1.00       Li        30      0.70 0.30                                Z2      1.00       Li        80      0.20 0.80                                AA1     1.00       Zn        50      0.50 0.50                                N       1.15       --        0       1.15 --                                  BB1     1.15       Li        50      0.58 0.57                                BB2     1.15       Li        66      0.39 0.76                                CC1     1.15       Na        55      0.52 0.63                                P       1.40       --        0       1.40 --                                  DD1     1.40       Li        46      0.76 0.64                                Q       0.1        --        0       0.10 --                                  EE1     0.1        Li        60      0.04 0.06                                S       1.3        --        0       1.3  --                                  FF1     1.3        Li        8       1.20 0.10                                T       2.6        --        0       2.6  --                                  GG1     2.6        Li        52      1.25 1.35                                ______________________________________                                    

EXAMPLE 4 Effect of Rubber Content on Blend Impact Properties

In this example, the impact strengths and flexural modulus of moldedtest pieces of various polyester blend compositions were measured. Thethermoplastic polyester used in this example was a commercial PBT,Valox® 310, a molding grade polyester obtained from General Electric.Prior to all processing steps, the PBT and its blends were dried at 60°C. for four (4) hours under vacuum with a nitrogen purge.

Blends of PBT with both unmodified and modified block copolymer wereprepared in a 30 mm diameter corotating twin screw extruder. The blendcomponents were premixed by tumbling in polyethylene bags, and then fedinto the extruder. The extruder melt temperature profile was about 230°C. in the feed zone, about 240° C. in the barrel, and about 240° C. atthe die. A screw speed of 300 rpm was used. The extrudate waspelletized. Injection molded test specimens were made from pelletizedextrudate using an Arburg injection molder (Model number 221-55-250).Injection temperatures and pressures of about 220° C. to about 240° C.and about 800 psig to about 1200 psig, respectively, were employedduring the processing operations. The formulations and physicalproperties are shown in Table 4. Therein, samples "01" through "07" arecontrols.

As is readily apparent from Table 4, the addition of the modified blockcopolymers (U1 and DD1) significantly increases the impact strength ofthe polyester PBT. Additionally, improvements in the impact toughness ofthe modified block copolymer/polyester blends are surprisingly achievedwithout significantly sacrificing or compromising its flexural modulus(05, 06 and 07 versus 12, 14 and 16). Furthermore, the addition of atleast about 15 percent by weight of the modified block copolymerproduces a super-tough polyester blend material. A material is definedto be "super-tough" when the room temperature impact strength determinedusing ASTM-256 exceeds 10 ft-lb/in and a ductile failure is observed(test specimen does not break). As is readily apparent from FIG. 1, adistinct brittle to ductile failure transition is observed between 10and 15 percent by weight of the modified block copolymer in the blendcomposition (Curve I of FIG. 1), whereas no such transition occurs inthe blend containing the unmodified block copolymer (Curve II of FIG.1).

                                      TABLE 4                                     __________________________________________________________________________    Composition                                                                          Unmodified                                                                          Modified                                                                            1/8" Dry as Molded                                                Block Block Notched Izod  Flexural                                            Copolymer                                                                           Copolymer                                                                           (ft-lb/in)    Modulus                                      Sample                                                                            PBT                                                                              A  C  U1 DD1                                                                              R.T.                                                                              -20° F.                                                                     -40° F.                                                                     (Kpsi)                                       __________________________________________________________________________    01  100                                                                              -- -- -- -- 0.9 0.8  0.7  335                                          02  90 10 -- -- -- 0.9 --   --   --                                           03  80 20 -- -- -- 1.4 --   --   --                                           04  70 30 -- -- -- 1.7 --   --   --                                           05  90 -- 10 -- -- 1.6 0.9  0.8  305                                          06  80 -- 20 -- -- 2.2 1.2  1.2  280                                          07  70 -- 30 -- -- 2.9 1.3  1.2  230                                          08  90 -- -- 10 -- 2.0 --   --   --                                           09  80 -- -- 20 -- >19.9.sup.a                                                                       --   --   --                                           10  70 -- -- 30 -- >21.5.sup.a                                                                       --   --   --                                           11  95 -- -- --  5 1.1 0.9  --   312                                          12  90 -- -- -- 10 2.0 1.1  --   279                                          13  85 -- -- -- 15 >13.0.sup.a                                                                       1.9  --   240                                          14  80 -- -- -- 20 >18.0.sup.a                                                                       2.6  --   220                                          15  75 -- -- -- 25 >19.8.sup.a                                                                       3.3  --   199                                          16  70 -- -- -- 30 >19.9.sup.a                                                                       4.1  --   176                                          __________________________________________________________________________     .sup.a Ductile failure.                                                  

EXAMPLE 5 Effect of Counterion on Blend Properties

As in Example 4, the impact strengths and flexural modulus of similarlyprepared molded test pieces of various polyester blend compositions weremeasured. PBT (Valox® 310 from General Electric) and PET (Cleartuf®7207CS from Goodyear Chemical) were utilized as the polyesters. Thecompositions had a fixed block copolymer to polyester ratios of 20:80and 30:70. The samples prepared utilized the respective polyester(controls), the base block copolymers "C" and "D" (controls) and themodified block copolymer with carboxyl functionality (content) ofbetween 1.0% to 1.18% w having the counterions H¹⁺ (N), Li¹⁺ (X1, Z1, Z2and BB1), Na¹⁺ (CC1) and Zn²⁺ (AA1).

Table 5 depicts the effect of different counterions on the impactstrength as a function of temperature and on the flexural modulus of therespective materials. The monovalent metal (Li and Na) containingcarboxylate salts appeared to outperform the divalent metal (Zn)containing carboxylate salt in the blend compositions (18, 20, 21, 22,and 23 versus 19.) Furthermore, it appears that super-tough propertiesare detrimentally affected by metal ions having an available positivevalence state greater than one (1), at least in PET blends. Theunmodified block copolymer and the zinc carboxylate salt version of themodified block copolymer were comparable in modifying the impactperformance of the polyester (19 versus 06, 07 and 25). Here theopportunity presents itself wherein the blend composition may betailored to specific impact modification requirements by utilizing aspecific metal counterion and/or combination of metal counterions withor without the acid form of the modified block copolymer.

                                      TABLE 5                                     __________________________________________________________________________                      Sample                                                      Composition (% w) 17  18   19 20  21   22   23  01 24 06 07 25                __________________________________________________________________________    Polyester:                                                                    PBT                           70  70            100   80 70                   PET               80  80   80          80   80     100      70                             %                                                                Block Functionality                                                                        Neutral-                                                         Copolymer                                                                           (% w)  ization                                                          N     1.15    0   20                                                          BB1   1.15   50       20                                                      AA1   1.0    50            20                                                 CC1   1.15   55               30                                              X1    1.18   49                   30                                          Z1    1.0    30                        20                                     Z2    1.0    80                             20                                C     --     --                                       20 30                   D     --     --                                             30                Metal Counterion  --  Li   Zn Na  Li   Li   Li  -- -- -- -- --                Flexural Modulus (Kpsi)                                                                         208 246  210                                                                              --  175  242  216 335                                                                              406                                                                              280                                                                              230                                                                              241               1/8" Dry as Molded                                                            Notched Izod (ft-lb/in)                                                       Room Temperature  >21.1.sup.a                                                                       >18.2.sup.a                                                                        1.6                                                                              >20.2.sup.a                                                                       >21.1.sup.a                                                                        >21.3.sup.a                                                                        >15.9.sup.a                                                                       0.9                                                                              0.5                                                                              2.2                                                                              2.9                                                                              1.2               -20° F.    --  1.1  0.6                                                                              --  5.0  1.0  --  0.8                                                                              -- 1.2                                                                              1.3                                                                              --                -40° F.    --  1.0  0.6                                                                              --  3.2  1.9  --  0.7                                                                              -- 1.2                                                                              1.2                                                                              --                __________________________________________________________________________     .sup.a Ductile Failure                                                   

EXAMPLE 6 Effect of Degree of Neutralization on Blend Properties

In this example, the impact strengths and flexural moduli of molded testspecimens of various polyester blend compositions were measured. Herein,the degree of neutralization (metal carboxylate salt content) was variedto measure the corresponding effect on these properties at polyester toblock copolymer ratios of 80:20 and 70:30. Furthermore, the measurementswere performed on two different polyesters, PBT (Valox® 310) and PET(Cleartuf® 7207 CS). Specimens utilizing only PBT (01), PET (24), a70:30 and 80:20 ratio of PBT to unmodified block copolymer (04 and 07,30 and 06), and a 70:30 ratio of PET to unmodified block copolymer (25)were prepared as controls.

As is readily apparent from Tables 6, 7 and 8, the effect of the degreeof neutralization of the modified block copolymer on the impactproperties of the respective polyester blend is substantial.

Furthermore, with respect to super-tough properties, the effect of thedegree of neutralization of the modified block copolymer is unexpectedlyunique as between PBT and PET, both of which are poly(alkyleneterephthalates).

Poly(butylene terephthalate) (PBT)

As depicted in FIG. 2 (curve I) and tabulated in Table 6, 70:30PBT/modified block copolymer blend compositions of the present inventionexperience two brittle to ductile failure transitions. The firsttransition is observed between 0% and 20% (2.5% which is about 5%)neutralization (i.e., metal carboxylate salt concentration with respectto total carboxyl group functionality in the respective modified blockcopolymer which is incorporated in the respective PBT blend). The secondtransistion is observed between 55% and 100% (about 85%) neutralization.Thus, for super-toughening a 70:30 PBT/modified block copolymer blend,the effective degree of neutralization ranges from about 5% to about85%.

As depicted in FIG. 3 and tabulated in Table 7, 80:20 PBT/modified blockcopolymer blend compositions of the present invention also experiencetwo brittle to ductile failure transitions. The first transition isobserved between 0% and 20% (3.0% which is about 5%) neutralization. Thesecond transition is observed between 55% and 100% (about 80%)neutralization. Thus, for super-toughening a 80:20 PBT/modified blockcopolymer blend, the effective degree of neutralization ranges fromabout 5% to about 80%.

Now referring to curve I on FIG. 1, a brittle to ductile failuretransition, dependent primarily on the block copolymer content of thePBT blend, is indicated at 14% w (about 15% w) modified block copolymercontent. Therein, the respective modified block copolymers wereneutralized to 25% and 46%, respectively. With the above-referencedinformation tabulated in Table 8, FIG. 4 was constructed. FIG. 4indicates that at the minimum block copolymer content required forsuper-toughening PBT the effective degree of neutralization ranges fromabout 5% to about 75%.

Poly(ethylene terephthalate) (PET)

On the other hand, as depicted in FIG. 5 and tabulated in Table 9, PETblend compositions of the present invention apparently may onlyexperience one brittle to ductile failure transition. This transition isbelieved to occur between 80% and 100% neutralization, probably about95% neutralization. (See curve I of FIG. 5). Thus, the effective degreeof neutralization for super-toughening PET is at most about 95%,preferably from about 0% to about 90%, and more preferably from about 0%to about 80%.

Polyesters in general

Be that as it may, an improvement of the impact properties of articlesmanufactured from the polyester blends of the present invention isachieved over those impact properties achieved when utilizing therespective polyester alone or in a blend with the respective unmodified(base) block copolymer. Such improvement is achieved over the entirerange of neutralization (i.e., from 0% to 100%), regardless of the metalion utilized in neutralizing the carboxyl groups grafted thereto.

However, the optimum level of impact modification (i.e., super-toughmaterials) is experienced when the ductile failure mechanism is present.As the data herein indicates, the neutralization range needed to inducethe change in the mode of failure from brittle to ductile is quitedistinct. Thus, precise determination of this transition is easily andreadily determinable for modified block copolymers containing more orless carboxyl group functionality, different polyesters, differentpolyesters to block copolymer ratios and different metal counterions byperforming the ASTM-256-1/8' notched izod impact test on specimensprepared from these various compositions. As such, the impactmodification of polyesters utilizing these modified block copolymers maybe controlled through the neutralization process prior to or duringblending operations.

                                      TABLE 6                                     __________________________________________________________________________                                          1/8" Dry as Molded                                                            Notched Izod                                                         Flexural Impact Toughness                        Block      Functional-                                                                         Neutraliza-                                                                         Metal Modulus  (ft-lb/in)                              Sample.sup.c                                                                       Copolymer                                                                           ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          (Kpsi)                                                                             RT.sup.b                                                                          -20° F.                                                                     -40° F.                     __________________________________________________________________________    01   --    --    --    --    335  0.9 0.8  0.7                                04   A     --    --    --    --   1.7 --   --                                 07   C     --    --    --    230  2.9 1.3  1.2                                26   L     1.39   0    --    174  3.8 1.0  0.8                                27   Y1    1.39  19    Li    190  >20.4.sup.a                                                                       3.2  2.4                                10   U1    0.40  25    Li    --   >21.5.sup.a                                                                       --   --                                 28   W1    0.33  33    Li    190  >21.3.sup.a                                                                       2.0  1.6                                16   DD1   1.40  46    Li    176  >19.9.sup.a                                                                       4.1  --                                 21   X1    1.18  49    Li    175  >21.1.sup.a                                                                       5.0  3.2                                20   CC1   1.15  55    Na    --   >20.2.sup.a                                                                       --   --                                 29   Y2    1.39  100   Li    204  5.4 1.7  1.4                                __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c This data was utilized in constructing curve I in FIG. 2. "01",        "04", and "07" are controls. Except for "01", all samples were formulated     as 70% PBT and 30% block copolymer.                                      

                                      TABLE 7                                     __________________________________________________________________________                                          1/8" Dry as Molded                                                            Notched Izod                                                         Flexural Impact Toughness                        Block      Functional-                                                                         Neutraliza-                                                                         Metal Modulus  (ft-lb/in)                              Sample.sup.c                                                                       Copolymer                                                                           ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          (Kpsi)                                                                             RT.sup.b                                                                          -20° F.                                                                     -40° F.                     __________________________________________________________________________    01   --    --    --    --    335  0.9 0.8  0.7                                30   A     --    --    --    --   1.4 --   --                                 06   C     --    --    --    280  2.2 1.2  1.2                                31   G     0.40   0    --    --   2.0 --   --                                 09   U1    0.40  25    Li    --   >19.9.sup.a                                                                       --   --                                 14   DD1   1.40  46    Li    220  >18.0.sup.a                                                                       2.6  --                                 32   U2    0.40  100   Li    --   4.3 --   --                                 __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c This data was utilized in constructing FIG. 3. "01", "30", and "06     are controls. Except for "01", all samples were formulated as 80% PBT and     20% block copolymer.                                                     

                  TABLE 8                                                         ______________________________________                                                               1/8" Dry as Molded                                                            Notched Izod                                           Block         Neutral- lmpact Toughness                                       Copolymer     ization  (ft-lb/in)                                             Sample.sup.a                                                                          (% w)     (%)      RT    -20° F.                                                                       -40° F.                        ______________________________________                                        33      30.sup.a  2.5      10.0  --     --                                    34      20.sup.b  3.0      10.0  --     --                                    35      14.sup.c  35       10.0  --     --                                    36      14.sup.c  46       10.0  --     --                                    37      20.sup.b  80       10.0  --     --                                    38      30.sup.a  85       10.0  --     --                                    ______________________________________                                         .sup.a Data obtained from FIG. 2.                                             .sup.b Data obtained from FIG. 3.                                             .sup.c Data obtained from FIG. 1.                                        

                                      TABLE 9                                     __________________________________________________________________________                                      1/8" Dry as Molded                                                            Notched Izod                                                             Flexural                                                                           Impact Toughness                            Block      Functional-                                                                         Neutraliza-                                                                         Metal Modulus                                                                            (ft-lb/in)                                  Sample.sup.c                                                                       Copolymer                                                                           ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          (Kpsi)                                                                             RT.sup.b                                                                          -20° F.                                                                     -40° F.                     __________________________________________________________________________    24   --    --    --    --    406  0.5 --   --                                 25   D.sup.d                                                                             --    --    --    241  1.2 --   --                                 17   N     1.15   0    --    208  >21.1.sup.a                                                                       --   --                                 22   Z1    1.0   30    Li    242  >21.3.sup.a                                                                       1.0  1.0                                18   BB1   1.15  50    Li    246  >18.2.sup.a                                                                       1.1  1.1                                23   Z2    1.0   80    Li    216  >15.9.sup.a                                                                       --   --                                 39   Z1.sup.d                                                                            1.0   30    Li    242  >21.0.sup.a                                                                       1.5  1.1                                __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c This data was utlizied in constructing Curve I of FIG. 5. "24" and     "25" are controls. Except for "24", "25" and "39", all samples were           formulated as 80% PET and 30% block copolymer.                                .sup.d "25" and "39" were formulated as 70% PET and 30% block copolymer       and are presented herein for comparative purposes.                       

EXAMPLE 7 Effect of Degree of Functionality on Blend Properties

In this example, the impact strength of molded test specimens of variouspolyester blend compositions were measured. Herein, at a fixed polyesterto block copolymer ratio (a ratio of 80:20 for PET and a ratio of 70:30for PBT) and at approximately equal neutralization levels utilizinglithium as the metal counterion, the degree of functionality (carboxylgroup content) was varied to measure the corresponding effect on theimpact strength of the respective compositions. Specimens utilizing PBT(01) and, PET (24), a 70:30 ratio of PBT to unmodified block copolymer(07) and a 70:30 ratio of PET to unmodified block copolymer (25) wereprepared as controls.

As is evident from Table 10 and FIGS. 2 and 4, increasing the degree ofcarboxyl functionality in the modified block copolymer results in adramatic improvement in the impact strength of the polyester blendcomposition. A transition from a brittle to ductile failure mechanism isalso observed. As is quite apparent from Tables 10 and 11 for PBT andPET blends of the present invention, respectively, the minimum degree offunctionalization effective for super-toughening these PET and PBTblends is at least 0.25% w carboxyl functional groups based on the baseblock copolymer. However, a general improvement in the impact propertiesof such blends, say over the respective polyester alone, is achievedwith functionality levels as low as 0.1% w, and believed as low as 0.02%w, carboxyl functional groups based on the base block copolymer. Thus,for this general improvement, it is believed that the effective level offunctionality ranges from at least 0.02% w, preferably from about 0.02%w to about 20% w, preferably 0.1% w to about 10% w, and more preferablyfrom about 0.2% w to about 5% w, of the grafted carboxyl functionalgroups based on the base block copolymer.

Thus, the foregoing indicates that a minimum amount of grafting and/orstrong interaction is required to obtain the desired phase size whichtranslates in part into improved impact properties. Therefore, thedegree of functionality of the modified block copolymer provides anothermeans by which impact modification of polyesters may be controlled.

                                      TABLE 10                                    __________________________________________________________________________                                      1/8" Dry as Molded                                                            Notched Izod                                                             Flexural                                                                           Impact Toughness                            Block      Functional-                                                                         Neutraliza-                                                                         Metal Modulus                                                                            (ft-lb/in)                                  Sample.sup.c                                                                       Copolymer                                                                           ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          (Kpsi)                                                                             RT.sup.b                                                                          -20° F.                                                                     -40° F.                     __________________________________________________________________________    01   --    --    --    --    335  0.9 0.8  0.7                                07   C     --    --    --    230  2.9 1.3  1.2                                10   U1    0.40  25    Li    --   >21.5.sup.a                                                                       --   --                                 28   W1    0.33  33    Li    190  >21.3.sup.a                                                                       2.0  1.6                                41   V1    0.22  55    Li    213  3.1 1.3  1.2                                20   CC1   1.15  55    Na    --   >20.2.sup.a                                                                       --   --                                 21   X1    1.18  49    Li    175  >21.1.sup.a                                                                       5.0  3.2                                40   H     0.22   0    --    208  2.9 1.3  1.2                                42   V2    0.22  100   Li    213  5.6 1.3  1.2                                __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c Except for "01", all samples were formulated at 70% PBT and 30%        block copolymer. Samples "01" and "07" are controls. Samples "40", "41",      and "42" having a functionality of 0.22% w were utilized to construct         curve II on FIG. 2.                                                      

                                      TABLE 11                                    __________________________________________________________________________                                      1/8" Dry as Molded                                                            Notched Izod                                                             Flexural                                                                           Impact Toughness                            Block      Functional-                                                                         Neutraliza-                                                                         Metal Modulus                                                                            (ft-lb/in)                                  Sample.sup.c                                                                       Copolymer                                                                           ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          (Kpsi)                                                                             RT.sup.b                                                                          -20° F.                                                                     -40° F.                     __________________________________________________________________________    24   --    --    --    --    406  0.5 --   --                                 25   D.sup.d                                                                             --    --    --    241  1.2 --   --                                 43   Q     0.1    0    --    244  2.0 0.7  0.7                                44   R     0.5    0    --    255  >18.1.sup.a                                                                       1.2  1.2                                45   FF1   1.3    8    Li    262  >15.0.sup.a                                                                       1.7  1.4                                46   EE1   0.1   60    Li    257  2.0 0.7  0.7                                18   BB1    1.15 50    Li    246  >18.2.sup.a                                                                       1.1  1.0                                22   Z1    1.0   30    Li    242  >21.3.sup.a                                                                       1.0  1.0                                39   Z1.sup.d                                                                            1.0   30    Li    242  >21.0.sup.a                                                                       1.5  1.1                                __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature (23° C.).                                      .sup.c Except for "24", "25" and "39", all samples were formulated at 80%     PET and 20% block copolymer. "24" and "25" are controls. Samples "43" and     "46" having a functionality of 0.1% w were utilized to construct curve II     on FIG. 5. It should be noted that samples "43", "44", "45" and "46"          utilized diblock copolymers. However, these polymers are presently            believed to be adequate for the purpose of generally determining a minimu     effective functionality for supertoughening PET blends.                       .sup.d "25" and "39" were formulated as 70% PET and 30% block copolymer       and are presented herein for comparative purposes.                       

EXAMPLE 8 Effect of Different Polyesters on Blend Composition

In this example, the impact strengths and flexural moduli of molded testspecimens of various polyester blend compositions were measured. Herein,at a fixed polyester to block copolymer ratio of 80:20, the measurementswere performed on two different polyester systems. The polyestersutilized were PBT (Valox® 310 from General Electric) and PET (Cleartuf®7207 CS from Goodyear). Additionally, the degree of neutralization wasvaried to the measure the corresponding effect on these properties.Specimens utilizing only the respective polyester and a 80:20 ratio ofpolyester to unmodified block copolymer were prepared as controls.

Blends of the respective polyesters with both unmodified and modifiedblock copolymer were prepared in a 30 mm diameter corotating twin screwextruder. The blend components were premixed by tumbling in polyethylenebags and then fed into the extruder.

For PET blends, the extruder melt temperature profile was about 235° C.in the feed zone, about 245° C. in the barrel and about 240° C. at thedie. A screw speed of about 300 rpm was used. Injection molded testspecimens were made from pelletized extrudate using an Arburg injectionmolder (Model number 221-25-250). Injection temperatures and pressuresof about 260° C. to about 280° C. and about 800 psig to about 1000 psig,respectively, were employed during the processing operation.

For PBT blends, the extruder melt temperature profile was about 220° C.in the feed zone, about 245° C. in the barrel and about 215° C. at thedie. A screw speed of about 300 rpm was used. Injection molded testspecimens were made from pelletized extrudate using an Arburg injectionmolder (Model number 221-55-250). Injection temperatures and pressuresof about 240° C. to about 270° C. and about 600 psig to about 1000 psig,respectively, were employed during the processing operations.

As is readily apparent from Table 12, the effect of the degree ofneutralization of the modified block copolymer on the impact propertiesof a polyamide blend is dependent on the particular polyester and thelevel of --COOH present in the blend. At comparable carboxylfunctionality level in the modified polymer, PET blends maintainsuperior impact properties over a wider range of neutralization levelsthan PBT blends (32 versus 23). Be that as it may, improvements inimpact resistance are achieved throughout the entire range ofneutralization levels regardless of the particular polyester(s) utilizedin the blend (32 versus 01 and 06; 23 versus 24 and 25). Therefore, avariety of toughened polyester blends compositions differing in theirrespective degree of toughness may be achieved by varying (1) thepolyester or mixtures thereof and/or (2) the level of functionality, thedegree of neutralization, and/or modified polymer content, therebyeffectively varying the level of carboxyl functional groups and/or--COOH present in the blend.

                                      TABLE 12                                    __________________________________________________________________________                                                   1/8" Dry as Molded                                                            Notched Izod                                   Block                     Flexural                                                                           Impact Toughness                         Block Copolymer                                                                           Functional-                                                                          Neutraliza-                                                                         Metal  Modulus                                                                            (ft-lb/in)                     Sample.sup.c                                                                       Polyester                                                                          Copolymer                                                                           (% w) ity (% w)                                                                            tion (%)                                                                            Counterion                                                                           (Kpsi)                                                                             RT.sup.b                                                                           -20° F.                                                                     -40°          __________________________________________________________________________                                                             F.                   01   PBT  --     0    --     --    --     335  0.9  0.8  0.7                  06   PBT  C     20    --     --    --     280  2.2  1.2  1.2                  07   PBT  C     30    --     --    --     230  2.9  1.3  1.2                  14   PBT  DD1   20     1.40  46    Li     220  >18.0.sup.a                                                                        2.6  --                   31   PBT  G     20    0.4     0    --     --   2.0  --   --                   09   PBT  U1    20    0.4    25    Li     --   >19.9.sup.a                                                                        --   --                   32   PBT  U2    20    0.4    100   Li     --   4.3  --   --                   24   PET  --     0    --     --    --     406  0.5  --   --                   25   PET  D     30    --     --    --     241  1.2  --   --                   18   PET  BB1   20     1.15  50    Li     246  >18.2.sup.a                                                                        1.1  1.0                  17   PET  N     20     1.15   0    --     208  >21.1.sup.a                                                                        --   --                   22   PET  Z1    20    1.0    30    Li     242  >21.3.sup.a                                                                        1.0  1.0                  23   PET  Z2    20    1.0    80    Li     216  >15.9.sup.a                                                                        --   --                   __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c Samples "01", "06", "07", "24" and "25" are controls.             

EXAMPLE 9 Effect of Molecular Architecture of Modified Block Copolymeron Blend Compositions

In this example, the impact strengths and flexural moduli of molded testspecimens of various polyester blend compositions were measured. Herein,at a fixed PET (Cleartuf® 7202 CS) to block copolymer ratio of 80:20 andat a fixed PBT (Valox® 310) to block copolymer ratio of 70:30, themolecular architecture of the modified block copolymer was varied tomeasure the corresponding effect on these properties. Furthermore, themeasurements were performed on systems wherein the degree ofneutralization was also varied. Specimens utilizing only PBT (01), PET(24), and a 70:30 ratio of PBT to unmodified triblock copolymer (07)were prepared as controls.

As is readily apparent from Table 13, the addition of the modified blockcopolymer regardless of molecular architecture and degree ofneutralization increases the impact strength of the polyester.Furthermore and unexpectedly, modified diblock and modified triblockcopolymers are substantially equivalent with respect to super-tougheningpolyester--be it PBT or PET. (PBT: "47" versus "16"; and PET: "44" and"45" versus "17," "22," "18," and "23"). Unmodified diblock copolymers(A-B) have not typically been regarded as impact property improvers dueto their inherent inability to form a physically cross-linked networkwithin itself as do triblock copolymers (A-B-A). Thus, selection and/orblending of various modified block copolymers provide another means ofcontrolling the impact modification of the respective polyester(s).

                                      TABLE 13                                    __________________________________________________________________________                                                   1/8" Dry as Molded                                                            Notched Izod                                   Block                     Flexural                                                                           Impact Toughness                         Block Copolymer                                                                           Functional-                                                                          Neutraliza-                                                                         Metal  Modulus                                                                            (ft-lb/in)                     Sample.sup.c                                                                       Polyester                                                                          Copolymer                                                                           (% w) ity (% w)                                                                            tion (%)                                                                            Counterion                                                                           (Kpsi)                                                                             RT.sup.b                                                                           -20° F.                                                                     -40°          __________________________________________________________________________                                                             F.                   01   PBT  --     0    --     --    --     335  0.9  0.8  0.7                  07   PBT  C     30    --     --    --     230  2.9  1.3  1.2                  16   PBT  DD1   30     1.40  46    Li     176  >19.9.sup.a                                                                        4.1  --                   47   PBT  GG1   30     2.60  52    Li     210  >18.8.sup.a                                                                        3.0  2.5                  24   PET  --     0    --     --    --     406  0.5  --   --                   17   PET  N     20     1.15   0    --     208  >21.1.sup.a                                                                        --   --                   22   PET  Z1    20    1.0    30    Li     242  >21.3.sup.a                                                                        1.0  1.0                  18   PET  BB1   20     1.15  50    Li     246  > 18.2.sup.a                                                                       1.0  1.0                  23   PET  Z2    20    1.0    80    Li     216  >15.9.sup.a                                                                        --   --                   43   PET  Q     20    0.1     0    --     244  2.0  0.7  0.7                  46   PET  EE1   20    0.1    60    Li     257  2.0  0.7  0.7                  44   PET  R     20    0.5     0    --     255  >18.1.sup.a                                                                        1.2  1.2                  45   PET  FF1   20    1.3     8    Li     262  >15.0.sup.a                                                                        1.7  1.4                  __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature.                                                      .sup.c Samples "01", "24" and "07" are controls.                         

EXAMPLE 10 Effect of Phase Size on Blend Properties

In this example, the sensitivity of polyester blend properties to thephase size of the block copolymer therein was evaluated. Theformulations utilized were those indicated in Table 14.

A review of the results shown in Table 14 demonstrate the interplay ofthe various variables involved in super-toughening the respectivepolyester blends. These variables are block copolymer content (% w basedon block copolymer plus polyester), carboxyl group functionality (% wbased on the respective block copolymer), neutralization level (% ofcarboxyl functional groups), and phase size.

As earlier indicated, the minimum amount of carboxyl group functionalityeffective in super-toughening PBT and PET blends is at least about 0.25%w. For example, see samples "43" and "44" in Table 14. Though samples"08," "26," and "29" meet this limitation, these samples are notsuper-tough. Sample "08" does not have the minimum required blockcopolymer content of 14% w (about 15% w). Samples "26" and "29" do nothave the required neutralization level for super-toughening PBT (betweenabout 5% to about 85% neutralization; for PET: between about 0% to about80% neutralization).

Phase size, whether it be for a cell or a discrete particle, has beenenumerated as a variable affecting the super-toughening of polyesters.At this point, it should be noted that higher sheer (twin screw)extruders were utilized during blending operations herein. Thus, it isforeseeable that under low sheer conditions improper blending of thepolyester and block copolymer phases may result in a reduction, if notnegation, of these super-tough properties. From Table 14, it is observedthat phase sizes ranging from about 0.48 μm to about 0.7 μm areeffective in super-toughening PBT blends and from about 0.25 μm to about0.5 μm are effective in super-toughening PET blends. Thus, it ispresently believed that the effective phase size for super-tougheningPBT blend ranges from about 0.4 μm to about 0.7 μm and forsuper-toughening PET blends range from about 0.2 μm to about 0.5 μm.

                                      TABLE 14                                    __________________________________________________________________________                                                     1/8" Dry as Molded                                                            Notched Izod                                Block                             Impact Toughness             Poly-    Block Copolymer.sup.e                                                                      Functional-                                                                         Neutraliza-                                                                         Metal Phase Size (μm)                                                                     (ft-lb/in)                   Sample.sup.d                                                                       ester                                                                             Copolymer                                                                           (% w)  ity (% w)                                                                           tion (%)                                                                            Counterion                                                                          Mean                                                                              Sm/Lg.sup.c                                                                        RT.sup.b                                                                          -20° F.                                                                     -40°         __________________________________________________________________________                                                              F.                  02   PBT A     10     --    --    --    6.3  5/17                                                                              0.9 --   --                  03   PBT A     20     --    --    --    4.0  3/12                                                                              1.4 --   --                  04   PBT A     30     --    --    --    6.7  5/20                                                                              1.7 --   --                  07   PBT C     30     --    --    --    1.2 0.1/10                                                                             2.9 1.3  1.2                 08   PBT U1    10     0.40  25    Li    0.5 0.3/1.6                                                                            2.0 --   --                  09   PBT U1    20     0.40  25    Li    0.7 0.4/2.5                                                                            >19.9.sup.a                                                                       --   --                  10   PBT U1    30     0.40  25    Li    0.7 0.4/2.0                                                                            >21.5.sup.a                                                                       --   --                  26   PBT L     30     1.39   0    --    1.1 0.1/4.0                                                                            3.8 1.0  0.8                 27   PBT Y1    30     1.39  19    Li    0.48                                                                              0.05/1.6                                                                           >20.4.sup.a                                                                       3.2  2.4                 29   PBT Y2    30     1.39  100   Li    0.33                                                                              0.05/2.5                                                                           5.4 1.7  1.4                 44   PET R     20     0.5    0    --    0.50                                                                              --   >18.1.sup.a                                                                       1.2  1.2                 18   PET BB1   20     1.15  50    Li    0.45                                                                              --   >18.2.sup.a                                                                       1.1  1.0                 45   PET FF1   20     1.3    8    Li    0.25                                                                              --   >15.0.sup.a                                                                       1.7  1.4                 43   PET Q     20     0.1    0    --    0.30                                                                              --   2.0 0.7  0.7                 __________________________________________________________________________     .sup.a Ductile failure (no break).                                            .sup.b Room Temperature (23° C.).                                      .sup.c SM  Smallest phase size observed; Lg  Largest phase size observed.     .sup.d Samples "02", "03", "04" and "07" are controls. Samples "43", "44"     and "45" utilized modified diblock copolymers.                                .sup.e Polyester makes up the remainder.                                 

With these effective phase size ranges in mind, it is noted that samples"08" and "43" are not super-tough. However, sample "08" does not meetthe effective block copolymer content required for super-tougheningpolyester blends. Additionally, sample "43" does not meet the effectiveamount of carboxyl functionality for super-toughening the polyesterblends. Thus, it is quite apparent from the foregoing that the smallestphase size does not by itself always give the best results with respectto super-toughening.

As an additional observation, it is noted that as the neutralizationlevel is increased at a fixed functionality level, there iscorresponding reduction in the phase size of the block copolymer. (Seesamples "26", "27" and "29" in Table 14). Furthermore, at comparableneutralization levels, it also appears that as carboxyl groupfunctionality increases there is a corresponding reduction in the phasesize of the block copolymer ("27" versus "09" and "45" versus "44").Finally, as between the modified block copolymer and the unmodified(base) block copolymer, there again is a corresponding reduction ofphase size of the block copolymer when the modified block copolymer isincorporated into the blend as opposed to the unmodified blockcopolymer. (See Table 14 generally.)

Thus, phase size provides another means for controlling the impactmodification of the polyester.

EXAMPLE 11 Effect of Heat and UV Aging

In this example, the sensitivity of the polyester blend compositions ofthe present invention to heat and ultraviolet light (UV) were evaluated.For testing purposes, the composition was a 70:30 ratio of polyester(PBT, Valox® 310) to block copolymer "DD1", which contains 1.4% wcarboxyl functional groups of which 46% are neutralized with lithiumions.

The following test methods were utilized for heat and UV aging,respectively:

Heat Aging: Test specimens were exposed in an air circulating oven for72 hours at 150° C. This procedure is based on the General Motors testGM-7001-M for heat resistance of plastic molding compounds.

UV Aging: Test specimens were exposed in a carbon arc weatherometer to acycle which includes UV light, heat, and water spray for 360 hours. Thisis a version of the sunlight resistance test listed in UL 1581. Cam #7was used to control the water spray cycle.

As is readily apparent from Table 15, the polyester blends of thepresent invention are able to maintain their properties (impactresistance) even after severe heat and UV aging. Such is particularlytrue of the super-tough properties of the PBT blends of the presentinvention. ("48" and "49" versus "16.")

                  TABLE 15                                                        ______________________________________                                                              1/8" Dry as Molded                                                            Notched lzod                                            Block        Aging    Impact Toughness (ft-lb/in)                             Sample.sup.c                                                                         Copolymer Method   RT.sup.b                                                                             -20° F.                                                                       -40° F.                        ______________________________________                                        01     --        --       0.9    0.8    0.7                                   16     DD1       --       >19.9.sup.a                                                                          4.1    --                                    48     DD1       Heat     >17.9.sup.a                                                                          >5.3.sup.a                                                                           --                                    49     DD1       UV       >19.2.sup.a                                                                          2.4    --                                    ______________________________________                                         .sup.a Ductile failure.                                                       .sup.b Room Temperature (23° C.).                                      .sup.c Samples "48" and "49" 0.5% w Irganox ® 1010, a phenolic            antioxidant available from Ciba Geigy.                                   

EXAMPLE 12 Effect of Carboxyl Functional Group Graft Location

In this example, the sensitivity of a particular polyester blendcomposition to the graft location of the carboxyl functional group(i.e., grafting in the alkenyl arene block versus the selectivelyhydrogenated conjugated diene block) was evaluated. The composition wasof a 70:30 ratio of polyester (PBT, Valox® 310) to a partiallyneutralized modified block copolymer. The results are tabulated in Table16.

Three types of modified block copolymers were utilized. One of these isthe modified block copolymers utilized in the present invention, i.e.,grafted in the alkenyl arene blocks of the block copolymer. The othertwo were modified by grafting maleic anhydride and acrylic acid to theconjugated diene block, respectively prepared as follows:

COMPARATIVE POLYMER 1 (CP1) Maleic Anhydride Grafted

The base block copolymer "D" was extruder functionalized with 1.2% wbound maleic anhydride by the method disclosed in U.S. Pat. No.4,578,429, wherein maleic anhydride is grafted to the selectivelyhydrogenated conjugated diene block of the copolymer "D" via a freeradically initiated reaction. Unbound maleic anhydride was removed fromthis polymer by precipitating a cyclohexane solution of it into IPA.Thereafter, one pound of the maleic anhydride grafted block copolymerproduct was dissolved in THF to form a one gallon solution. Next, 4.08grams of lithium hydroxide dissolved in 100 ml of water was addedthereto. The partially neutralized maleic anhydride grafted polymer(CP1) was coagulated into water, and then water washed to ph7 to removeunreacted lithium hydroxide. Water was then removed by vacuum drying. Aninfrared spectrum of the polymer (CP1) showed a broad salt band at1550-1600 cm⁻¹, but did not exhibit either maleic anhydride or maleicacid peaks to any appreciable extent. These peaks are found at 1790 cm⁻¹and 1750 cm.sup. -1, respectively. Titration with potassium methoxide(as earlier disclosed herein) indicated that about 78% of the acidgroups (--COOH) had been neutralized. This partially neutralized polymer(CP1) as extruder blended with PBT (Valox® 310) according to theprocedure disclosed herein at a 70:30 ratio of polyester to blockcopolymer. Except for the low residual ethylenic unsaturation in thebase block copolymer and the utilization of high shear extruders (twinscrew) in both the grafting and blending stages, such blends are similarto those of Shiraki et al (U.S. Pat. No. 4,657,971). This comparativeblend (CB1) had a 1/8 inch notched izod at room temperature of only 1.1ft-lb/in.

COMPARATIVE POLYMER 2 (CP2) Acrylic Acid Grafted

The base block copolymer "D" was extruder functionalized with 1.6% wbound acrylic acid by the method disclosed in U.S. Pat. No. 4,578,429,wherein acrylic acid is grafted to the selectively hydrogenatedconjugated diene block of the copolymer "D" via a free radicallyinitiated reaction. Unbound acrylic acid was removed from this polymerby precipitating a cyclohexane solution of it into IPA (isopropylalcohol). Thereafter, 300 grams of this polymer was redissolved incyclohexane to make a one gallon solution. Next, 1.4 grams of lithiumhydroxyide dissolved in 30 ml of water was added to the polymersolution. The partially neutralized polymer (CP2) was precipitated intoIPA and then vacuum dried. An infrared spectrum of the polymer (CP2)showed a broad salt band centered at approximately 1600 cm⁻¹. Titrationwith potassium methoxide (as earlier disclosed herein) indicated thatabout 62% of the acid groups (--COOH) had been neutralized. Thispartially neutralized polymer (CP2) was extruder blended with PBT(Valox® 310) according to the procedure disclosed herein at a 70:30ratio of polyester to block copolymer. Again, except for the lowresidual ethylenic unsaturation in the base block copolymer and theutilization of high shear extruders (twin screw) in both the graftingand blending steps, such blends are similar to those of Shiraki et al.(U.S. Pat. No. 4,657,971). This comparative blend (CB2) has a 1/8 inchnotched izod at room temperature of only 2.9 ft-lb/in.

COMPARISON

Thus, as is readily apparent in Table 16, the neutralization effectwhich manifests itself in PBT blends with carboxyl functional groupsgrafted to the alkenyl arene blocks of the polymers herein does notmanifest itself in PBT blends with carboxyl functional groups grafted tothe selectively hydrogenated conjugated diene blocks of the same baseblock copolymer. Therefore, the blends of the present invention aretruly distinct and unique. Furthermore, the super-tough PBT blends ofthe present invention are also unique and unexpected.

                                      TABLE 16                                    __________________________________________________________________________                                     No. of                                                                        Carboxyl Groups     Room                                                                          Temperature.sup.b            Base  Location                                                                             Type            per Base Neutral-   1/8" Notched Izod            Block of     of       Functionality                                                                        Copolymer                                                                              ization                                                                            Metal Impact Toughness         Sample                                                                            Copolymer                                                                           Functionality.sup.c                                                                  Functionality                                                                          (% w).sup.d                                                                          Molecule (%).sup.e                                                                          Counterion                                                                          (ft-lb/in)               __________________________________________________________________________    CP1 D     B      Grafted Maleic                                                                         1.2    12.6     78   Li    1.1                                       Anhydride                                                    CP2 D     B      Grafted Acrylic                                                                        1.6    11.4     62   Li    2.9                                       Acid                                                         20  D     A      Carboxyl Group                                                                         1.15   13.2     55   Na    >20.2.sup.a              16  D     A      Carboxyl Group                                                                         1.4    16.0     46   Li    >19.9.sup.a              21  C     A      Carboxyl Group                                                                         1.18   13.0     49   Li    >21.1.sup.a              27  C     A      Carboxyl Group                                                                         1.39   15.4     19   Li    >20.4.sup.a              28  B     A      Carboxyl Group                                                                         0.33   13.3     33   Li    >21.3.sup.a              10  A     A      Carboxyl Group                                                                         0.40    5.9     25   Li    >21.5.sup.a              __________________________________________________________________________     .sup.a Ductile failure.                                                       .sup.b Room Temperature (23° C.).                                      .sup.c B  selectively hydrogenated conjugated diene block; A  alkenyl         arene block.                                                                  .sup.d Based on base block copolymer.                                         .sup.e Percent of total carboxyl functional groups which have been ionize     by neutralization with a metal ion.                                      

While the present invention has been described and illustrated byreference to particular embodiments thereof, it will be appreciated bythose of ordinary skill in the art that the same lends itself tovariations not necessarily illustrated herein. For this reason, then,reference should be made solely to the appended claims for purposes ofdetermining the true scope of the present invention.

What is claimed is:
 1. A process for producing a toughened polymericcomposition having an Izod impact greater than 10 ft-lb/in comprisingthe steps of:(a) providing a functionalized selectively hydrogenatedblock copolymer comprising,(i) at least on polymer block A, block Abeing predominantly a polymerized alkenyl arene block, (ii) at least oneselectively hydrogenated polymer block B, block B being predominantly apolymerized block of at least one conjugated diene, and (iii) graftedpredominantly to the A blocks on the average of from one carbonyl groupfor each 44 alkenyl arene monomer units to one carboxyl group for each6.6 alkenyl arene monomer units; (b) acidifying the functionalizedselectively hydrogenated block copolymer by contacting thefunctionalized selectively hydrogenated block copolymer with an organicacid to form an acidified functionalized selectively hydrogenated blockcopolymer; (c) neutralizing a portion of the acidified functionalizedselectively hydrogenated block copolymer by contacting the acidifiedfunctionalized selectively hydrogenated block copolymer with an amountof metal salt effective to neutralize from about 19 mole percent toabout 55 mole percent of the carboxylic acid functionality of theacidified functionalized block copolymer to form a partially neutralizedfunctionalized block copolymer; (d) blending the partially neutralizedfunctionalized block copolymer with a thermoplastic polymer compositioncomprising poly(1,4-butylene terephthalate) wherein the thermoplasticpolymer is present in a weight ratio of about 50:50 up to about 85:15relative to the functionalized hydrogenated block copolymer; and (e)recovering a toughened polymeric composition.
 2. The process accordingto claim 1, wherein the functionalized block copolymer has a linearstructure.
 3. The process according to claim 1, wherein(a) each of the Ablocks prior to being hydrogenated is predominantly a polymerizedmonoalkenyl monocyclic arene block having an average molecular weight ofabout 1,000 to about 125,000, (b) each of the B blocks prior to beinghydrogenated is predominantly a polymerized conjugated diene blockhaving an average molecular weight of about 10,000 to about 450,000, (c)the A blocks constituting about 1 to about 99 percent by weight of thebase block copolymer, (d) the residual ethylenic unsaturation of the Bblock is less than about 10 percent of the ethylenic unsaturation of theB block prior to being hydrogenated, and (e) the residual aromaticunsaturation of the A blocks is greater than about 50 percent of thearomatic unsaturation of the A block prior to being hydrogenated.
 4. Theprocess according to claim 3, wherein the A blocks constitute about 2 toabout 60 percent by weight of the base block copolymer.
 5. The processaccording to claim 4, wherein said A blocks constitute about 2 to about40 percent by weight of said base block copolymer.
 6. The processaccording to claim 3, wherein prior to being hydrogenated:(a) the Ablock is polymerized styrene and (b) the B block is selected from thegroup consisting of polymerized isoprene, polymerized butadiene, andpolymerized isoprene and butadiene copolymer.
 7. The process accordingto claim 6, wherein the polymerized styrene block has an averagemolecular weight within the range of about 1,000 and about 60,000.